Active Tectonics

Over 80 new fault plane solutions, combined with satellite imagery as well as both modern and historical observations of earthquake faulting, are used to investigate the active tectonics of the Middle East between western Turkey and Pakistan.The deformation of the western part of this region is dominated by the movement of continental material laterally away from the Lake Van region in eastern Turkey. This movement helps to avoid crustal thickening in the Van region, and allows some of the shortening between Arabia and Eurasia to be taken up by the thrusting of continental material over oceanic-type basement in the southern Caspian, Mediterranean, Makran and Black Sea. Thus central Turkey, bounded by the North and East Anatolian strike-slip faults, is moving west from the Van region and overrides the eastern Mediterranean at two intermediate depth seismic zones: one extending between Antalya Bay and southern Cyprus, and the other further west in the Hellenic Trench. The motion of northern Iran eastwards from the Van region is achieved mainly by a conjugate system of strike-slip faults and leads to the low angle thrusting of Iran over the southern Caspian Sea. The seismicity of the Caucasus shows predominantly shortening perpendicular to the regional strike, but there is also some minor elongation along the strike of the belt as the Causcasus overrides the Caspian and Black Seas.The deformation of the eastern part of this region is dominated by the shortening of Iran against the stable borders of Turkmenistan and Afghanistan. The north-east direction of compression seen in Zagros is also seen in north-east Iran and the Kopet Dag, where the shortening is taken up by a combination of strike-slip and thrust faulting. Large structural as well as palaeomagnetic rotations are likely to have occurred in NE Iran as a result of this style of deformation. North-south strike-slip faults in southern Iran allow some movement of material away from the collision zone in NE Iran towards the Makran subduction zone, where genuinely intermediate depth seismicity is seen.Within this broad deforming belt large areas, such as central Turkey, NW Iran (Azerbaijan), central Iran and the southern Caspian, appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200-300 km wide. The motion of these blocks can usefully be described by poles of rotation. The poles presented in this paper predict motions consistent with those observed and also predict the opening of the Gulf of Iskenderun NE of Cyprus, the change within the Zagros mountains from strike-slip faulting in the NW to intense thrusting in the SE, and the relatively feeble seismicity in SE Iran (Baluchistan). This description also explains why the north-south structures along the Iran-Afghanistan border do not cut the east-west ranges of the Makran.Within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation, even though motions at the surface may be concentrated on faults. The evolution of fault systems within the active zones is controlled by geometric constraints, such as the requirement that simultaneously active faults do not, in general, intersect.Many of the active processes discussed in this paper, particularly large-scale rotations and lateral movement along the regional strike, are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them.

Turkey forms one of the most actively deforming regions in the world and has a long history of devastating earthquakes. The better understanding of its neotectonic features and active tectonics would provide insight, not only for the country but also for the entire Eastern Mediterranean region. Active tectonics of Turkey is the manifestation of collisional intracontinental convergence-and tectonic escape-related deformation since the Early Pliocene (∼5 Ma). Three major structures govern the neotectonics of Turkey; they are dextral North Anatolian Fault Zone (NAFZ), sinistral East Anatolian Fault Zone (EAFZ) and the Aegean-Cyprean Arc. Also, sinistral Dead Sea Fault Zone has an important role. The Anatolian wedge between the NAFZ and EAFZ moves westward away from the eastern Anatolia, the collision zone between the Arabian and the Eurasian plates. Ongoing deformation along, and mutual interaction among them has resulted in four distinct neotectonic provinces, namely the East Anatolian contractional, the North Anatolian, the Central Anatolian 'Ova' and the West Anatolian extensional provinces. Each province is characterized by its unique structural elements, and forms an excellent laboratory to study active strike-slip, normal and reverse faulting and the associated basin formation.

Inferring principal stress directions from geologic data, focal mechanisms, and in situ stress measurements, we have prepared a map of principal horizontal stress orientations for the conterminous United States. Stress provinces with linear dimensions which range between 100 and ...

Seismicity and fault-plane solutions show that the active deformation in the Adriatic region is very varied. West of Messina, N-S shortening occurs with slip vectors representative of the overall Africa-Eurasia motion. Along the length of peninsular Italy, NE-SW extension on normal faults is the dominant style of deformation, but changes t o N-S shortening in N. Italy. Inland central and northern Yugoslavia is deforming on strike-slip and thrust faults, and an intense belt of NE-SW shortening continues south along the coast from central Yugoslavia into Albania. South of Albania the shortening in coastal regions is in a more easterly direction. The most remarkable feature of the region is the low level of seismicity in the Adriatic Sea itself, compared with the intense activity in the hgh topographic belts that border it on the SW, NW and NE. The relatively rigid behaviour of the Adriatic allows its motion relative t o Eurasia to be described by rotation about a pole in N. Italy. Anticlockwise rotation about this pole accounts, in a general way, for the change in style and orientation of the deformation in the circum-Adriatic belts. Historical and recent seismicity account for approximately equal rates of extension in central Italy and shortening in southern Yugoslavia of about 2 mm yr-' ; however, these are uncertain by at least a factor of two, and are anyway likely t o be underestimates of the true motion, because of the unknown contribution of aseisniic creep.

The south Caspian intracontinental depression, floored by oceanic basement, is a relatively stable block, with minor deformation, surrounded by active fold-thrust belts of arcuate form (Talesh, Alborz, and Kopeh Dagh Mountains), which have undergone intense late Cainozoic crustal shortening. The basin is interpreted as a Neogene-Quaternary "compressional depression," bounded by multi-role mountain-bordering reverse faults, and apparently floored by a late Paleozoic -Triassic or late Mesozoic -early Tertiary "modified oceanic crust" trapped along an old geosuture. It may be a relic of an old (Paleozoic-Triassic) ocean, or else a marginal sea developed behind a Mesozoic-Paleogene ocean, and analysis of geological and geophysical data enables a scheme to be suggested. The general arcuate shape of the Alborz and the Talesh bordering mountain belts follows the pattern of the supposed rigid and thickened ocean crust of south Caspian depression.

Longitudinal profiles along sixteen major transverse Himalayan rivers add important constraints to models of active continental subduction and its evolution. These profiles are characterized by a zone of relatively high gradient that cannot be associated with differential resistence to erosion in all cases. The base of the zone of increased gradients correlates with (1) the topographic front between the Lesser and High Himalayas, (2) the narrow belt of intermediate-magnitude thrust earthquakes, (3) the Main Central Thrust zone (MCT). These features define a small circle in the central portion of the Himalayan arc.

The Zagros mountains of SW Iran are one of the most seismically active intra-continental fold-and-thrust belts on Earth, and an important element in the active tectonics of the Middle East. Surface faulting associated with earthquakes is extremely rare, and so most information about the active faulting comes from earthquakes. We use long-period teleseismic P and SH body waves to determine the orientation and depth of faulting in 16 new earthquakes, and then evaluate and synthesize all the available teleseismic data on earthquake source parameters in the Zagros. We use this information to investigate the style and distribution of active faulting in the Zagros, and how it contributes to the N–S shortening of the Arabia–Eurasia collision. When the data are ranked in quality and carefully evaluated, simple patterns are seen that are not apparent when routine catalogue data are taken at face value. An important change in the fault configuration occurs along strike of the belt. In the NW, overall convergence is oblique to the trend of the belt and the surface anticlines, and is achieved by a spatial separation (‘partitioning’) of the orthogonal strike-slip and shortening components on separate parallel fault systems. By contrast, in the SE, overall convergence is orthogonal to the regional strike and achieved purely by thrusting. In the central Zagros, between these two structural regimes, deformation involves parallel strike-slip faults that rotate about vertical axes, allowing extension along the strike of the belt. The overall configuration is similar to that seen in other curved shortening belts, such as the Himalaya and the Java–Sumatra trench. All the Zagros earthquakes we have been able to check have centroids shallower than ∼20 km and are confined to the upper crust. Many of the larger earthquakes are likely to occur in the basement beneath the sedimentary cover, which is active even beneath areas of known shallow structural decollement such as the Dezful embayment. The dominant style of shortening is high-angle reverse faulting with dips >30° though some lower-angle thrusting occurs in places. Active thrust and reverse faulting is relatively confined to the lower topography on the SW edge of the belt today, and only strike-slip faulting affects the higher topography. Profound vertical changes in structural and stratigraphic level indicate that a similar style of deformation was once active across the width of the Simple Folded Belt, but has progressively migrated SW over the last 5 Ma. There is no evidence for a seismically active structural decollement, such as a low-angle thrust, beneath the Zagros, nor is there any seismic evidence for active subduction, either beneath the Zagros or beneath central Iran. Instead the Arabian margin seems to have shortened by distributed thickening of the basement. Only in the syntaxis of the Oman Line, at the SE end of the Zagros, is there any evidence for a low-angle thrust of regional extent. Here, earthquakes continue 50  km north of the Zagros Thrust Line (the geological suture between the Arabian margin and central Iran) reaching depths of ∼30 km, and may represent thrusting of Arabian basement beneath central Iran to this extent.

The unique and evolving nature of the Precambrian geological environment in many ways was responsible for significant differences between Precambrian clastic sedimentary deposits and their Phanerozoic-modern equivalents. Some form of plate tectonics, with rapid microplate collisions and concomitant volcanic activity, is inferred to have led to the formation of greenstone belts. Explosive volcanism promoted common gravity-flow deposits within terrestrial greenstone settings, with braided alluvial, wave=storm-related and tidal coastline sediments also being preserved. Late Archaean accretion of greenstone terranes led to emergence of proto-cratons, where cratonic and rift sedimentary assemblages developed, and these became widespread in the Proterozoic as cratonic plates stabilised. Carbonate deposition was restricted by the paucity of stable Archaean terranes.

3: summarizing 20 years of research on Italy's earthquake geology. Tectonophysics, 453. Basili R., Kastelic V. and Tiberti M.M., 2010. Seismogenic sources in the studied key areas (contributing to populate the DISS). Final report of INGV-DPC 2007-2009 Project "Analysis of the seismic potential in Italy for the evaluation of the seismic hazard". Basili R. and D'Ambrogi C., 2010. Provenance of the Amatrice Basin (central Apennines) infill: implications for the long-term activity of the Mt. Gorzano fault. Abstract for the 85th Congresso SGI, Pisa, 6-8 Sep 2010. Di Bucci D., Burrato P., Vannoli P., Fracassi U. and Valensise G., 2010. Seismogenic faults and their surface signature: insights from the 2009 L'Aquila earthquake (Central Apennines, Mw 6.3) for the understanding the adjacent areas. Submitted to Terra Nova. Maesano F., D'Ambrogi C., Burrato P. and Toscani G., 2010. Long-term geological slip rates of the Emilia thrust front (N Apennines) from 3D modeling of key buried horizons. Abstract for the 85th Congresso SGI, Pisa, 6-8 Sep 2010. Tiberti M.M., Burrato P., Basili R., Vannoli P., Kastelic V. and Fracassi U., in preparation. New evidence of Holocene raised beaches in the Crotone Peninsula (Calabrian Arc, Southern Italy). Vannoli P., Basili R., Tiberti M.M., Burrato P.,

Quaternary tectonics and paleoseismologicalinvestigations have defined a reliable framework ofactive faults in the southern Umbria and AbruzziApennines. Two sets of NW–SE to NNW–SSE trending, 16to 33 km-long, normal and normal-oblique faults orfault systems have caused the displacement of LatePleistocene–Holocene deposits and landforms within theinvestigated sector. Available data on verticaloffsets indicate that both Late Pleistocene–Holoceneand Quaternary (since the later part of the EarlyPleistocene; 0.9–1 Ma) slip rates range between 0.4and 1.2 mm/yr (range 0.6–0.8 mm/yr preferred).Paleoseismological investigations show that recurrenceintervals for surface faulting events are alwaysgreater than 1,000 years and are usually greater than2,000 years. Both paleoseismological data andlong-term seismicity show that activation of theinvestigated faults may result in earthquakes ofM = 6.5–7.0. The extension rate across the two sets ofprimary faults ranges between 0.7 and 1.6 mm/yr.Horizontal seismic strain has been calculated to be0.5–0.6 mm/yr, based on the summation of the seismicmoment of M > 5.3 earthquakes which have affected theinvestigated area since 1200 AD. This value may belower than that inferred through geological data,probably because the seismological record reliable forthe addition of the seismic moments covers a too shorttime window (about 800 years) to be consideredrepresentative of the tectonic activity in theinvestigated area. This conclusion iscorroborated by the large recurrence intervalper fault (>1,000–2,000 years) inferred frompaleoseismological analysis. A comparison of theactive-fault framework and historical-seismicitydistribution indicates that the entire eastern set ofactive faults has likely not been activated since 1000AD, thus indicating that the elapsed time since thelast activation for several faults of the investigatedarea may be greater than 1,000 years. In terms ofhazard, the highest probability of activation isrelated to the eastern set faults, due to theobservation that the elapsed time for some of thesefaults may be similar to the recurrence interval. Asan example, paleoseismological andarchaeoseismological data indicate that the elapsedtime for the Mt. Vettore and Mt. Morrone Faults may begreater than 1,650 and 1,850 years, respectively.These data may have significant implications for riskrelated to a number of towns in central Italy and tothe city of Rome. As for the latter, in fact,monumental heritage has suffered significant damagedue to earthquakes of M > 6.5 which originated in theinvestigated Apennine sector.

Nepal can be divided into the following ®ve east±west trending major tectonic zones. (i) The Terai Tectonic Zone which consists of over one km of Recent alluvium concealing the Churia Group (Siwalik equivalents) and underlying rocks of northern Peninsular India. Recently active southward-propagating thrusts and folds beneath the Terai have aected both the underlying Churia and the younger sediments. (ii) The Churia Zone, which consists of Neogene to Quaternary foreland basin deposits and forms the Himalayan mountain front. The Churia Zone represents the most tectonically active part of the Himalaya. Recent sedimentologic, geochronologic and paleomagnetic studies have yielded a much better understanding of the provenance, paleoenvironment of deposition and the ages of these sediments. The Churia Group was deposited between H14 Ma and H1 Ma. Sedimentary rocks of the Churia Group form an archive of the ®nal drama of Himalayan uplift. Involvement of the underlying northern Peninsular Indian rocks in the active tectonics of the Churia Zone has also been recognised. Unmetamorphosed Phanerozoic rocks of Peninsular India underlying the Churia Zone that are involved in the Himalayan orogeny may represent a transitional environment between the Peninsula and the Tethyan margin of the continent. (iii) The Lesser Himalayan Zone, in which mainly Precambrian rocks are involved, consists of sedimentary rocks that were deposited on the Indian continental margin and represent the southernmost facies of the Tethyan sea. Panafrican diastrophism interrupted the sedimentation in the Lesser Himalayan Zone during terminal Precambrian time causing a widespread unconformity. That unconformity separates over 12 km of unfossiliferous sedimentary rocks in the Lesser Himalaya from overlying fossiliferous rocks which are >3 km thick and range in age from Permo-Carboniferous to Lower to Middle Eocene. The deposition of the Upper Oligocene±Lower Miocene¯uvial Dumri Formation records the emergence of the Himalayan mountains from under the sea. The Dumri represents the earliest foreland basin deposit of the Himalayan orogen in Nepal. Lesser Himalayan rocks are less metamorphosed than the rocks of the overlying Bhimphedis nappes and the crystalline rocks of the Higher Himalayan Zone. A broad anticline in the north and a corresponding syncline in the south along the Mahabharat range, as well as a number of thrusts and faults are the major structures of the Lesser Himalayan Zone which is thrust over the Churia Group along the Main Boundary Thrust (MBT). (iv) The crystalline high-grade metamorphic rocks of the Higher Himalayan Zone form the backbone of the Himalaya and give rise to its formidable high ranges. The Main Central Thrust (MCT) marks the base of this zone. Understanding the origin, timing of movement and associated metamorphism along the MCT holds the key to many questions about the evolution of the Himalaya. For example: the question of whether there is only one or whether there are two MCTs has been a subject of prolonged discussion without any conclusion having been reached. The well-known inverted metamorphism of the Himalaya and the late orogenic magmatism are generally attributed to movement along the MCT that brought a hot slab of High Himalayan Zone rocks over the cold Lesser Himalayan sequence. Harrison and his co-workers, as described in a paper in this volume, have lately proposed a detailed model of how this process operated. The rocks of the Higher Himalayan Zone are generally considered to be Middle Cambrian to Late Proterozoic in age. (v) The Tibetan Tethys Zone is represented by Cambrian to Cretaceous-Eocene fossiliferous sedimentary rocks overlying the crystalline rocks of the Higher Himalaya along the Southern Tibetan Detachment Fault System (STDFS) which is a north dipping normal fault system. The fault has dragged down to the north a huge pile of the Tethyan sedimentary rocks forming some of the largest folds on the Earth. Those sediments are generally considered to have been deposited in a more distal part of the Tethys than were the Lesser Himalayan sediments.

Normal faulting which has developed since the Middle Pleistocene, with an overall ESE-WNW extension, is the dominant mode of deformation which has characterized the Calabrian arc up to the present. Quaternary normal faults extend for a total length of about 180 km along the inner side of the arc. The different normal fault segments, which, during the Pleistocene, controlled the evolution of the main marine sedimentary basins, are varying in length from 10 to 20 km and have fault escarpments showing a very young morphology which define the fronts of the major mountain ranges of the arc. The morphological features of the fault escarpments suggest slip rates of 0.8-1.1 mm/yr for the last 700 k.y. and values of 0.6-0.9 mm/yr for the last 120 k.y., indicating a uniform rate of faulting since the Middle Pleistocene. Crustal seismicity and the mesoseismic areas of historical large events (6.5 < M ~< 7.1) which occurred in the Calabrian arc are located within a narrow belt along the hanging walls of the Quaternary normal fault segments. This suggests that the normal faults which dissect the inner side of the Calabrian arc may be seismically active.

1] To investigate the kinematics of the Adriatic region, we integrate continuous and episodic GPS measurements with M w > 4.5 earthquake slip vectors selected from the Regional Centroid Moment Tensor catalogue. Coherent motion of GPS sites in the Po Valley, in Apulia, and in the Hyblean Plateau allows us to estimate geodetically constrained angular velocities for these regions. The predictions of the GPS-inferred angular velocities are compared with the earthquake slip vectors, showing that the seismically expressed deformation at the microplate boundaries is consistent with the observed geodetic motion. The remarkable consistency between geodetic, seismological, and geological evidence of active tectonics suggests that active deformation in the central Adriatic is controlled by the relative motion between the Adria and Apulia microplates. The microplates' angular rotation rates are then compared with the rotation rates calculated with a simple block model supporting the hypotheses (1) that Apulia forms a single microplate with the Ionian Sea and possibly with the Hyblean region and (2) that Adria and Apulia rotate in such a way as to accommodate the Eurasia-Nubia relative motion. We suggest that the present-day microplate configuration follows a recent fragmentation of the Adriatic promontory that during the Neogene rigidly transferred the Africa motion to the orogenic belts that now surround the Adriatic region.

The data sets, model parameterizations, and results from the five NGA models for shallow crustal earthquakes in active tectonic regions are compared. A key difference in the data sets is the inclusion or exclusion of aftershocks. A comparison of the median spectral values for strike-slip earthquakes shows that they are within a factor of 1.5 for magnitudes between 6.0 and 7.0 for distances less than 100 km. The differences increase to a factor of 2 for M5 and M8 earthquakes, for buried ruptures, and for distances greater than 100 km. For soil sites, the differences in the modeling of soil/sediment depth effects increase the range in the median long-period spectral values for M7 strike-slip earthquakes to a factor of 3. The five models have similar standard deviations for M6.5-M7.5 earthquakes for rock sites and for soil sites at distances greater than 50 km.

We present a new method for evaluating relative active tectonics based on geomorphic indices useful in evaluating morphology and topography. Indices used include: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf). Results from the analysis are accumulated and expressed as an index of relative active tectonics (Iat), which we divide into four classes from relatively low to highest tectonic activity.The study area along the southwest border of the Sierra Nevada in southern Spain is an ideal location to test the concept of an index to predict relative tectonic activity on a basis of area rather than a single valley or mountain front. The study area has variable rates of active tectonics resulting from the collision of Africa with Europe that has produced linear east–west anticlinal forms, as well as extension with variable vertical rates of normal faulting to about 0.5 m/ky. We test the hypothesis that areas of known, relatively high rates of active tectonics are associated with indicatives values of Iat.

Italy has one of the most complete and historically extensive seismic catalogues in the World due to a unique and uninterrupted flow of written sources that have narrated its seismic history since about the end of the Iron Age. Seismic hazard studies have therefore always been mainly based upon this huge mass of data. Nevertheless, the Italian catalogue probably "lacks" many M ≥ 6.5 events, the seismogenetic structures responsible for which are characterized by recurrence times that are longer than the time span covered by our historical sources. For these reasons, and as in other countries, earthquake data that in Italy have been derived from paleoseismological studies should finally become a necessary ingredient in seismic risk assessment. Indeed, over the past 20 years, some hundred trenches have been excavated, supplying reliable and conclusive data on the recent activities of many faults. Through to many robust datings of surface fault events, these studies have provided the ages of several unknown or poorly known M ≥ 6.5 earthquakes. Here, we summarize the state of the art of paleoseismology in Italy, and present a first catalogue of 56 paleoearthquakes (PCI) that occurred mainly in the past 6 kyr. The PCI integrates the historical/instrumental seismic catalogue, and extends it beyond the recurrence time of the seismogenetic faults (2000 ± 1000 yr). We feel confident that the use of the PCI will enhance future probabilistic seismic hazard assessment, and thus contribute to more reliable seismic risk mitigation programs.

1] We utilize topographic analysis of channel profiles combined with field measurements of erosion rates to explore the distribution of channel incision in the Anyemaqen Shan, a broad mountainous region in the northeastern Tibetan plateau. Tributary channels to the Yellow River display systematic downstream increases in channel gradient associated with convex upward longitudinal profiles. Steep lower reaches of channels are associated with rapid (>1 m/ka) incision rates along the Yellow River, while upstream reaches are associated with relatively slow (0.05-0.1 m/ka) erosion of soil-mantled uplands. Covariance between erosion rates and channel steepness indices suggest that channels are adjusted to match long-wavelength differential rock uplift across the range. Geologic constraints indicate that rapid incision downstream of the range is associated with excavation of basin fill driven by changes in relative base level farther downstream. The upstream limit of this wave of transient incision is marked by a series of knickpoints that are found at nearly the same elevation throughout the watershed, consistent with knickpoint migration as a kinematic, rather than diffusional, wave. Tributary channel gradients downstream of knickpoints, however, display a progressive adjustment to increased incision rates that may reflect the influence of increased sediment flux. Comparison of observed channel profiles to a stream power model of fluvial behavior reveals that the rate of knickpoint propagation can only be explained if the erosional efficiency coefficient (K) increases during incision. Our results thus highlight the utility of channel profile analysis to reconstruct the fluvial response to both active tectonism and external changes in base level.

We present detailed data of channel morphology for a river undergoing a transient response to active normal faulting where excellent constraints exist on spatial and temporal variations in fault slip rates. We show that traditional hydraulic scaling laws break down in this situation, and that channel widths become decoupled from drainage area upstream of the fault. Unit stream powers are ~4 times higher than those predicted by current scaling paradigms and imply that incision rates for rivers responding to active tectonics may be signifi cantly higher than those heretofore modeled. The loss of hydraulic scaling cannot be explained by increasing channel roughness and is an intrinsic response to tectonic forcing. We show that channel aspect ratio is a strongly nonlinear function of local slope and demonstrate that fault-induced adjustment of channel geometries has reset hillslope gradients. The results give new insight into how rivers maintain their course in the face of tectonic uplift and illustrate the fi rst-order control the fl uvial system exerts on the locus and magnitude of sediment supply to basins.

Since 1997 we maintain and systematically update the European-Mediterranean Regional Centroid Moment Tensor (RCMT) catalog, which contains seismic-moment tensors for earthquakes with moderate magnitude (4.5 < M < 5.5) in the Mediterranean and European regions. We present 354 new solutions for the period 2005-2008. The Catalog now spans 12 years and contains more than 1000 definitive RCMT solutions. In addition to definitive solutions, we maintain and update a dataset of recent 'quick' solutions that are computed soon after an earthquake occurs using the more limited set of data available in quasireal time. We investigate the reliability of the moment tensor results in the RCMT catalog. Comparison with Global CMT results, which is possible for the larger events (M < 5.0) in the RCMT catalog, shows that for 75% of the events, the Kagan angle measure of the similarity of two moment tensors is smaller than 20 • , reflecting good agreement of the results. We describe improvements and enhancements in the dissemination of the RCMT results through our web site.

The Sierra Nevada of the central Betic Cordillera is a 3000 m-high mountain range surrounded by Neogene-Quaternary sedimentary basins, having been uplifted since Late Miocene times. The southern and western mountain fronts of the Sierra Nevada are fault-bounded, while the northern one is an unconformity between the Neogene-Quaternary sediments of the Guadix-Baza basin and the metamorphic rocks of the Nevado-Filabride complex. We have carried out a geomorphic study by examining drainage patterns and characteristics of mountain fronts in order to reveal areal variations and styles of rock uplift. Mountain front sinuosity (S mf ), area-altitude relations (hypsometric curves), and valley floor entrenchment differ significantly between the northern, western, and southern mountain fronts. The lack of important faults along the northern Sierra Nevada mountain front, together with the elevated topographic position of the Guadix-Baza basin (average altitude is around 1100 m), points to similar uplift of both geomorphic units (sierra and basin) in a single large-scale crustal block. The asymmetry factors show systematic asymmetries at both sides of the Lanjarón River, probably due to the presence of an active NNE-SSW oriented antiform in the western Sierra Nevada. Finally, river profiles indicate maximal river entrenchment in the western part of the Sierra Nevada, probably related to the uplift of the footwall of the Padul-Nigüelas fault-system. Therefore, our geomorphic analysis suggests that the western part of the Sierra Nevada is tectonically active by means of a combination of normal faults along the mountain front and NNE-SSW oriented active folds, which, in turn, likely have a gravitational origin related to the exhumation of the footwall of the normal fault-system.

The central Apennines fault system (CAFS) of peninsular Italy, overprints earlier structures of a Neogene fold and thrust belt and includes segments characterized by diffuse seismicity distributed within a NNW-SSE-trending zone, 50-60 km wide. The system has been analysed by means of morphotectonic and structural analysis of exposed active fault segments. The resulting fault structure consists of an interconnecting network of roughly N-S-trending, left-lateral, strike-slip segments and mostly NW-SE-oriented, transtensional to normal faults. Evidence for recent activity of CAFS structures is provided by faulted Middle Pleistocene-Holocene deposits (including 30-40-ka-old pyroclastites and 40-ka-old palustrine sediments), fresh scarps in both bedrock and Late Quaternary continental deposits, and decametric lateral offsets locally affecting the post-Wurmian drainage pattern of the area. The regional stress field responsible for the development and evolution of the CAFS, as inferred from fault slip data, is characterized by a NW-SE compression and by a NE-SW extension. The CAFS pattern and its present-day kinematics have been related to left-lateral strike-slip motion on northsouth-trending crustal faults. The existence of deep-seated strike-slip faults in the central Apennines has implications for seismic hazard analysis. Motion along these structures suggests, in fact, that coseismic surface faulting is distributed, and that cumulative displacements include normal, transtensional, and strike-slip components. The seismogenic potential of CAFS structures can therefore be best described by multiple-rupture models and be better analysed in terms of partial contributions of lower-rank features constituting congruent structural associations within the system.

Mt. Etna is located along the east coast of Sicily, near the boundary between the continental crust of the Hyblean Plateau and the Mesozoic oceanic crust of the Ionian basin. The main active faults near Mt. Etna cut the base of its eastern flank, forming a 30 km long system of NNE- and NNW-trending, ene´chelon fault segments (the Acireale-Piedimonte system),

We examine the tectonic geomorphology of La Sila, Calabria, southern Italy, a high-standing (1500 m) plateau surrounded by crustal extension, with map, DEM, and field data. These data are used to constrain a simple geodynamic model that describes short-wavelength deformation of the plateau rim. Topographic metrics including drainage patterns, river longitudinal profiles, and swath profiles are consistent with field stratigraphic relationships collectively suggesting that local tectonic deformation is embedded within a broader, regional uplift that has increased the mean elevation of the Sila Plateau during the Quaternary. The concavity, steepness, and length-gradient index of modeled river longitudinal profiles proved to be the most useful metrics for recording the effects of locally active faults. A previously unrecognized horst on the northeastern portion of the plateau was identified with these data. Nevertheless, the core of the Sila Plateau remains relatively undeformed with respect to its flanks which are characterized by steep, fault-bounded escarpments. Active extension has dropped base level for and unloaded the plateau rim, causing deep fluvial incision and associated flexural uplift of the footwall. This footwall uplift helps maintain a separate external, and nearly radial drainage away from the plateau along its flanks, and a nearly closed drainage for the plateau interior. A drainage divide roughly correlates with the plateau rim, inhibiting the process of drainage integration through the Sila interior and subsequent landscape dissection. As a result, geomorphic processes driving erosion of the Sila upland are lagging behind the tectonic processes that have driven rock uplift leading to an overall increase in mean surface elevation. These results underscore the importance of the lag times a landscape may endure in transforming from one tectonic and base level condition to another. We conclude that the Calabrian forearc has a similar geomorphic evolution as the more northern Apennines consistent with the emerging view that growth of Apennine topography has been recent (Quaternary), rapid, and possibly decoupled from rock deformation in the orogenic wedge.

Recent results of high-resolution seismic tomography and mineral physics experiments are used to study mantle dynamics of Western Pacific and East Asia. The most important processes in subduction zones are the shallow and deep slab dehydration and the convective circulation (corner flow) processes in the mantle wedge. The combination of the two processes may have caused the back-arc spreading in the Lau basin, affected the morphology of the subducting Philippine Sea slab and its seismicity under southwest Japan, and contributed to the formation of the continental rift system and intraplate volcanism in Northeast Asia, which are clearly visible in our tomographic images. Slow anomalies are also found in the mantle under the subducting Pacific slab, which may represent (a) small mantle plumes, (b) upwellings associated with the slab collapsing down to the lower mantle, or (c) sub-slab dehydration associated with deep earthquakes caused by the reactivation of large faults preserved in the slab. Combining tomographic images and earthquake hypocenters with phase diagrams in the systems of peridotite+ water, we proposed a petrologic model for arc volcanism. Arc magmas are caused by the dehydration reactions of hydrated slab peridotite that supply water-rich fluids to the mantle wedge and cause partial melting of the convecting mantle wedge. A large amount of fluids can be released from hydrated MORB at depths shallower than 55 km, which move upwards to hydrate the wedge corner under the fore-arc, and never drag down to the deeper mantle along the slab surface. Slab dehydration reactions at 120 km depth are the antigorite-related 5 reactions which supply water-rich fluids for forming the volcanic front. Phase A and Mg-surssasite breakdown reactionsat 200 and 300 km depths below 700°C cause the second and third arcs, respectively. Moreover, the dehydration reactions of super-hydrous phase B, phases D and E at 500-660 km depths cause the fluid transportation to the mantle boundary layer (MBL) (410-660 km depth). The stagnant slabs extend from Japan to Beijing, China for over 1000 km long, indicating that the arc-trench system covers the entire region from the Japan trench to East Asia. We propose a big mantle wedge (BMW) model herein, where hydrous plumes originating from 410 km depth cause a series of intra-continental hot regions. Fluids derived from MBL accumulated by the double-sided subduction zones, rather than the India-Asia collision and the subsequent indentation into Asia, are the major cause for the active tectonics and mantle dynamics in this broad region.

Clay mineralogy and major-element geochemistry were investigated on 58 surface sediment samples collected in 27 rivers draining Malay Peninsula, Borneo, and Sumatra to assess the chemical weathering process and its controlling factors in tropical Southeast Asia. The clay mineral assemblages show high kaolinite contents in Malay Peninsula (average 80%), Sumatra (58-78%), and South Borneo (41-55%), high illite contents in North Borneo (47-77%), and moderate smectite contents in Sumatra (6-29%). Intensive chemical weathering is identified in all three investigated regions from both clay mineralogical and geochemical (bulk and clayfraction) results regardless of their various lithological and tectonic settings. Relatively, the chemical weathering intensity increases gradually from North Borneo to South Borneo, and further to Malay Peninsula and Sumatra. Our results suggest that the East Asian-Australian monsoon climatic condition with constant warm temperature and abundant precipitation throughout the year is the principal forcing factor on the chemical weathering, and the tectonic activity including mountain uplift, earthquakes, and volcanic eruptions and their specific lithological characters is only a subordinate factor on the intensity of chemical weathering in tropical Southeast Asia.

An inventory of the available surficial data on active faults in Italy has been compiled by gathering all the available information
on peninsular Italy (project by CNR, National Group for the Defense against Earthquakes), the central-eastern Alps and
the Po Plain (EC ‘PALEOSIS’ project). Such information has been summarised in maps (reporting surficial expressions of
faults with length L≥11 km) and in a table where fault parameters relevant for seismic hazard assessment (e.g. slip rates, recurrence
intervals for surface faulting events, etc..) have been reported. Based on the geological characteristics of the Italian
territory, a fault has been considered as active if it shows evidence of Late Pleistocene-Holocene displacements. Active faults
in Italy are distributed throughout the entire Apennine chain, in the Sicilian and Calabrian regions and in some Alpine sectors,
but knowledge is not homogeneously distributed through the territory. The largest amount of data is related to the central
Apennines. In contrast, fault geometries and parameters are less well defined in the southern Apennines, Sicily and Calabria,
where investigations have started more recently. Knowledge is sparse in the northern Apeninnes, where data necessary
to define fault parameters are lacking and also the chronology of the activity has to be considered cautiously. Abundant blind
faulting in the Po Plain hinders the detection of active faults by means of the classical surficial investigations and therefore the
present knowledge is limited to the Mantova fault. Blind faults and the peculiar recent geological history of the Alpine areas,
which is strongly conditioned by the erosional and depositional activity during and after the last glacial maximum, also hinder
the identification of active faults in the central-eastern Alps. Some faults in this Alpine sector are believed to be active, but data
on their segmentation are still missing. Available information indicates that Italian active faults are usually characterised by
slip rates lower than 1 mm/yr. Recurrence intervals for surface faulting events are longer than 1,000 years in the central and
southern Apennines. This review on the Italian active faults represents the first step to produce a map of the major seismic
sources in Italy, which in turn will result from the merge of surficial data with seismological and geological subsurficial data.
The available knowledge gathered in this paper indicates those areas where data are presently sparse. It should be, therefore,
possible to better plan future geomorphological and paleoseismological investigations.

We use drainage reconstructions to estimate long-term offsets on the Gowk fault, an oblique right-lateral strike-slip fault in eastern Iran, on which there have been a number of recent large earthquakes. A 3 km horizontal offset is inferred from well-preserved geomorphology. We further identify a total cumulative offset of ,12 km, which produces a simple reconstruction of geomorphology across the fault, ®lling in pull-apart basins, restoring rivers to linear courses across the fault trace and aligning structural and bed-rock features. The probable age of the Gowk fault, and K±Ar dating of offset basalts north of the study region, suggest an overall slip rate of ,1.5±2.4 mm/year. This is small compared with the overall 10±20 mm/year of shear expected between central Iran and Afghanistan and the de®cit is likely to have been accommodated on other faults east of the Gowk fault. Drainage displaced by dextral movement leads to the development of a series of basins along the fault and a longitudinal topographic pro®le that resembles an asymmetric saw-tooth. The geomorphic evolution of the fault zone at the surface includes both normal and reverse faulting components, re¯ecting a probable ramp-and-¯at structure in cross-section. This interpretation is consistent with evidence from the analysis of seismological, radar and surface rupture data in recent earthquakes. q

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 98, NO. B12, PAGES 21,809-21,821, DECEMBER 10, 1993 Statistical Physics Model for the Spatiotemporal Evolution of Faults PATIENCE A. COWIE,1 CHRISTIAN VANNESTE, AND DIDIER SORNETTE Laboratoire de Physique de ...

To provide a detailed record of a relatively rare thrust surface rupture and examine its active tectonic implications, we have conducted field mapping of the surface rupture associated with the 2005 M w 7.6 Kashmir earthquake. Despite the difficulty arising from massive earthquake-induced landslides along the surface rupture, we found that typical pressure ridges and warps extend northwestward for a distance of ∼70 km, with a northeast-side-up vertical separation of up to ∼7 m. Neither the main frontal thrust nor the main boundary thrust is responsible for the earthquake, but three active faults or fault segments within the Sub-Himalaya, collectively called the Balakot-Bagh fault, compose the causative fault. Although the fault exhibits substantial geomorphic expression of repeated similar surface ruptures, only a part of it had been mapped as active before the earthquake. The location of the hypocenter suggests that the rupture was initiated at a deep portion of the northern-central segment boundary and propagated bilaterally to eventually break all three segments. Our obtained surface rupture traces and the along-strike-slip distribution are both in good agreement with results of prompt analyses of satellite images, indicating that space geodesy can greatly aid in time-consuming field mapping of surface ruptures. Assuming that the extensive fill terrace in the meizoseismal area was abandoned during 10-30 ka, we tentatively estimate the earthquake recurrence interval and shortening rate on the Balakot-Bagh fault to be 1000-3300 yr and 1:4-4:1 mm=yr, respectively. These estimates indicate that the Balakot-Bagh fault is not a main player of Himalayan contraction accommodation. Ⓔ Selected field photographs and ArcGIS files of the mapped surface rupture traces and measured vertical separations are available in the electronic edition of BSSA.

Spatial variations of Quaternary deformation and tectonic activity of faults along the Acambay graben are assessed using geomorphic and morphometric approaches. The Acambay graben is an east-west trending structure of apparent Quaternary age, located in the central part of the Mexican Volcanic Belt, which gives rise to pronounced scarps over a distance of about 80 km. Continuing tectonic activity in the Acambay graben is confirmed by recent well documented seismic episodes.

The Pantanal is a tectonic depression located at the left margin of the Upper Paraguay River. The Paraguay is the trunk river of an alluvial depositional tract composed by several large marginal alluvial fans, the Taquari fan being the largest one. The present landscape is a complex tropical wetland characterized by month-long floods every year, with geomorphic features derived from the present conditions and others inherited from successive Pleistocene and Holocene climates. Some areas containing ponds are landscape relicts generated by eolian deflation during the Last Glacial Maximum. Many ponds, closed depressions isolated from the superficial waters by vegetated crescent ridges of fine sands, were interpreted as salt pans bordered by lunette sand dunes. Initiation of the modern wetland has occurred during the Pleistocene/Holocene transition, with the change to a more humid climate and the individualization of lacustrine systems. Active tectonics has been playing an important role in the development of the Pantanal landscape. Nowadays, the Paraguay River meanders in a large flood plain with extensive swamp surfaces, being structurally constrained by faults in the west border of the basin. Sedimentation within the Pantanal wetland is also affected by tectonic activity, especially along faults associated with the Transbrasiliano Lineament. r

Ambient noise tomography and multiple plane-wave earthquake tomography are new methods of surface wave analysis that yield much more highly refined information about the crust and uppermost mantle than traditional surface wave techniques. Applied together to data observed at more than 300 broad-band seismic stations from the Transportable Array component of the EarthScope USArray, these methods yield surface wave dispersion curves from 8 to 100 sec period across the entire western US with unprecedented resolution. We use the local Rayleigh wave phase speed curves to construct a unified isotropic 3D Vs model to a depth of about 150 km. Crustal and uppermost mantle features that underlie the western US are revealed in striking relief. As the USArray continues to sweep eastward across the US, the substructure of the entire country will be unveiled.

We present a new map of the present-day stress field in Italy obtained from all the available data. The map reports 200 horizontal stress directions inferred from 109 borehole breakout data, 44 centroid moment tensor solutions, 34 other focal mechanisms, most of which are from polarity distributions, seven stress inversions of microearthquake data, two averages of T and P axes of earthquake focal mechanisms in zones of diffuse seismic activity, and four fault slip data. The integration of breakout data, which yield horizontal stress directions, with fault plane solutions, which reflect the stress regime, allows us to obtain an improved map of the present-day stress in Italy. This stress field map can be used for a better comprehension of active tectonic processes, for seismic hazard assessment, and to foresee the behavior of faults recognized with other methods. Stress directions obtained from different data, although relative to different depth intervals (e.g., 0-7 km for breakouts and 0-20 km for most of the earthquakes) and to different tectonic units, are consistent. Since many regions in Italy are characterized by an extensional stress regime, we report the minimum horizontal stress (•hmin) orientations. The map shows that an extensional regime affects most of the Apenninic belt. Conversely, a compressional (or transpressional) regime characterizes the eastern Alps, the eastern side of the northern Apennines, and the southern Tyrrhenian to northern Sicily zone. An abrupt change in stress directions marks the transition between northern and southern Apennines, suggesting that the two arcs are characterized by a different tectonic setting and recent evolution. In this paper we report all the data analyzed to date, with their geographic coordinates and average stress directions, and we describe the main stress provinces in Italy in the framework of the tectonic evolution of the region.

This paper examines the relationship between seismogenic thickness, lithosphere structure and rheology in central and northeastern Asia. We accurately determine earthquake depth distributions which reveal important rheological variations in the lower crust. These variations exert a fundamental control on the active tectonics and the morphological evolution of the continents. We consider 323 earthquakes across the Tibetan Plateau, the Tien Shan and their forelands as well as the Baikal Rift, NE Siberia and the Laptev Sea and present the source parameters of 94 of these here for the first time. These parameters have been determined through body wave inversion, the identification of depth phases or the modelling of regional waveforms. Lower crustal earthquakes are found to be restricted to the forelands in areas undergoing shortening, and to locations where rifting coincides with abrupt changes in lithosphere thickness, such as the NE Baikal Rift and W Laptev Sea. The lower crust in these areas is seismogenic at temperatures that may be as high as 600°C, suggesting that it is anhydrous, and is likely to have great long-term strength. Lower crustal earthquakes are therefore a useful proxy indicating strong lithosphere in places that are too small in areal extent for this to be confirmed independently by estimating effective elastic thickness from gravity-topography relations. The variation in crustal rheology indicated by the distribution of lower-crustal earthquakes has many implications ranging from the support of mountain belts and the formation of steep mountain fronts, to the localization and orientation of rifting. In combination, these processes can also be responsible for the separation of the front of the thin-skinned mountain belts from their hinterlands when continents separate.

We document the structural context of the 1999 Chi-Chi earthquake (M w Z7.6) in western Taiwan, which is one of the best-instrumented thrust-belt earthquakes. The main surface break and large slip (3-10 m) is on two segments of the shallow otherwise aseismic beddingparallel Chelungpu-Sanyi thrust system, which shows nearly classic ramp-flat geometry with shallow detachments (1-6 km) in the Pliocene Chinshui Shale and Mio-Pliocene Kueichulin/Tungkeng Formations. However, rupture is complex, involving at least six faults, including a previously unknown deeper thrust (8-10 km) on which the rupture began. We compare the coseismic displacements with a new 3D map of the Chelungpu-Sanyi system. The displacements are spatially and temporally heterogeneous and well correlated with discrete geometric segments of the 3D shape of the fault system. Geodetic displacement vectors are statistically parallel to the nearest adjacent fault segment and are parallel to large-scale oblique fault corrugations. The displacement magnitudes are heterogeneous at several scales, which requires in the long term other non-Chi-Chi events or significant aseismic deformation. The Chelungpu thrust has a total displacement of w14 km but the area of largest Chi-Chi slip (w10 m) is on a newly propagated North Chelungpu Chinshui detachment (w0.3 km total slip) which shows abnormally smooth rupture dynamics. q

In this study we investigate the Late Cretaceous to recent tectonic evolution of the southwestern Baltic Sea based on a dense grid of seismic reflection profiles. This area covers the Baltic Sea sector of the salt influenced North German Basin and its transition to the salt free Baltic Shield across the Tornquist Zone. The Upper Cretaceous to recent structural evolution is discussed by means of individual seismic sections and derived high-resolution time-structure maps of the main horizons, i.e., the Upper Cretaceous, Tertiary and Pleistocene. The Upper Creta-ceous and Tertiary layers reveal numerous significant faults throughout the study area. Several of these faults propagate upwards across the unconsolidated Pleistocene sediments and occasionally penetrate the surface. The salt influenced North German Basin reveals three major fault trends: NW-SE, N-S and NNE-SSW. Several of these faults are located directly above basement (sub-salt) faults and salt pillows. The majority of these faults are trending N-S to NNE-SSW and parallel the direction of the Glückstadt Graben faults. In the salt free Tornquist Zone, we identify two major shallow fault trends, which are NW-SE and NE-SW. The majority of these faults are located above basement faults, following the direction of the Tornquist Zone. We conclude that generally basement tectonics controls activation and trends of shallow faults. If salt is present, the ductile salt layer causes a lateral shift between the sub-and supra-salt faults. Major plate reorganisation related to the Africa-Iberia-Europe convergence and the subsequent Alpine Orogeny caused reactivation of pre-existing faults and vertical salt movement in the Late Cretaceous. The change of stress orientation from NE-SW to a NW-SE during Neogene caused another phase of fault and salt tectonic reactivation. We explain that the ice-sheet loading and/or present day stress field may have acted in combination, causing the recent tectonics and upward extension of the faults.

Observations of active dike intrusions provide present day snapshots of the magmatic contribution to continental rifting. However, unravelling the contributions of upper crustal dikes over the timescale of continental rift evolution is a significant challenge. To address this issue, we analyzed the morphologies and alignments of >1500 volcanic cones to infer the distribution and trends of upper crustal dikes in various rift basins across the East African Rift (EAR). Cone lineament data reveal along-axis variations in the distribution and geometries of dike intrusions as a result of changing tectonomagmatic conditions. In younger (<10 Ma) basins of the North Tanzanian Divergence, dikes are largely restricted to zones of rift-oblique faulting between major rift segments, referred to here as transfer zones. Cone lineament trends are highly variable, resulting from the interplay between (1) the regional stress field, (2) local magma-induced stress fields, and (3) stress rotations related to mechanical interactions between rift segments. We find similar cone lineament trends in transfer zones in the western branch of the EAR, such as the Virunga Province, Democratic Republic of the Congo. The distributions and orientations of upper crustal dikes in the eastern branch of the EAR vary during continental rift evolution. In early-stage rifts (<10 Ma), upper crustal dikes play a limited role in accommodating extension, as they are confined to areas in and around transfer zones. In evolved rift basins (>10 Ma) in Ethiopia and the Kenya Rift, rift-parallel dikes accommodate upper crustal extension along the full length of the basin.

The identifi cation of individual past earthquakes and their characterization in time and space, as well as in magnitude, can be approached in many different ways with a large variety of methods and techniques, using a wide spectrum of objects and features. We revise the stratigraphic and geomorphic evidence currently used in the study of paleoseismicity, after more than three decades since the work by Allen (1975), which was arguably the fi rst critical overview in the fi eld of earthquake geology. Natural objects or geomarkers suitable for paleoseismic analyses are essentially preserved in the sediments, and in a broader sense, in the geologic record. Therefore, the study of these features requires the involvement of geoscientists, but very frequently it is a multidisciplinary effort. The constructed environment and heritage, which typically are the focus of archaeoseismology and macroseismology, here are left aside. The geomarkers suitable to paleoseismic assessment can be grouped based on their physical relation to the earthquake's causative fault. If directly associated with the fault surface rupture, these objects are known as direct or on-fault features (primary effects in the Environmental Seismic Intensity [ESI] 2007 scale). Conversely, those indicators not in direct contact with the fault plane are known as indirect or off-fault evidence (secondary effects in the ESI 2007 scale). This second class of evidence can be subdivided into three types or subclasses: type A, which encompasses seismically induced effects, including soft-sediment deformation (soil liquefaction, mud diapirism), mass movements (including slumps), broken (disturbed) speleothems, fallen precarious rocks, shattered basement rocks, and marks of degassing (pockmarks, mud volcanoes); type B, which consists of remobilized and redeposited sediments (turbidites,

Neotectonic structures distributed from the Goringe bank to the Tell Atlas mountains show that the Africa-Eurasia plate boundary in the western Mediterranean corresponds to an eastwest-trending deforming zone (Goringe-Alboran-Tell). Main Pliocene and Quaternary tectonic structures of the northern Atlas Mountains are northeast-southwest-striking fault-related folds, similar to that of El Asnam, and are related to north-south to northwest-southeast compressional movements. Active tectonics in agreement with the main seismicity distribution and focal mechanisms also support an oblique plate convergence and the existence of a 50 -100-km-wide transpression zone from Goringe, across Al-

The ϳ400 km 2 Clearwater River basin, located on the Pacific flank of the actively uplifting Olympic Mountains of western Washington State, contains a well-preserved flight of Holocene fluvial terraces. We have collected a large data set of numeric ages from these terraces that is used to elucidate the geomorphic, fluvial, active tectonic, and climatic processes that operate at Holocene spatial and temporal scales. Detailed field mapping reveals three prominent Holocene straths and their overlying terrace deposits. Terrace ages fall into three broad ranges: ca. 9000-11 000 yr B.P. (Qt4), 4000-8000 yr B.P. (Qt5), and 0-3000 yr B.P. (Qt6). Terrace deposit stratigraphy, sedimentology, and age distributions allow us to consider two alternative models for their genesis. The favored model states that the terrace ages are coincident with lateral incision of the Clearwater channel, emplacement of the terrace alluvium, and the carving of the straths. Vertical incision of the Clearwater channel was primarily relegated to the brief (ϳ1000 yr) intervals when we have no record of terraces. Alternatively, the straths were carved as the channel incised vertically during the brief time periods between dated terrace deposits, and the terrace ages record a subsequent long time of alluviation atop the straths and concomitant termination of vertical incision. In both models, we envision a Clearwater River channel at or near capacity with a temporally variable rate of both lateral and vertical incision. Small deviations from this at-capacity condition are *driven by variations in the liberation and delivery of hillslope sediment to the channel. We consider several causes for variable hillslope sediment flux in this tectonically active setting including Holocene climate change and ground accelerations related to earthquakes. Holocene rates of vertical incision are reconstructed along nearly the entire Clearwater Valley from the wide distribution of dated terraces. Incision rates clearly increase upstream, mimicking a pattern documented for Pleistocene terraces in the same basin; however, the rates are 2-3 times those determined for the Pleistocene terraces. The faster Holocene incision rates may be interpreted in terms of an increase in the rates of rock uplift. However, we favor an alternative explanation in which the Holocene rates represent a channel rapidly reacquiring its stable, graded concavity following protracted periods of time in the Pleistocene when it could not accomplish any vertical incision into tectonically uplifted bedrock because the channel was raised above the bedrock valley bottom by climatically induced alluviation. These results illustrate how, even in tectonically active settings, representative rates of rock uplift inferred from studies of river incision should be integrated over at least one glacial-interglacial cycle.

1] We integrate existing and new geologic data [REtreating TRench, Extension, and Accretion Tectonics (RETREAT project)], particularly on the origin, growth, and activity of the mountain front at Bologna, Italy, into a new model that explains Apennine orogenesis in the context of a slab rollback -upper plate retreat process. The Bologna mountain front is an actively growing structure driving rock uplift $1 mm/year, cored by a midcrustal flat-ramp structure that accommodates ongoing shortening driven by Adria subduction at a rate of $2.5 mm/year. The data we use are assembled from river terraces and associated Pleistocene growth strata, geodesy including releveling surveys, reinterpretation of published reflection lines, and a new high-resolution reflection line. These data constrain a simple trishear model that inverts for blind thrust ramp depth, dip, and slip. Apennine extension is recognized both in the foreland, as high-angle normal faults and modest stretching in the carapace of the growing mountain front, and in the hinterland, with larger normal faults that accomplish some crustal thinning as the upper plate retreats. This coevolution of extension and shortening shares some notable characteristics with other basement-involved collisional orogens including the early Tertiary Laramide orogeny in the American West and the Oligocene to Miocene evolution of the Alps. We propose a possible relationship between underplating and the development of the Po as a sag basin as a Quaternary phenomenon that may also apply to past periods of Apennine deformation (Tortonian). Continued shortening on the structure beneath the Bologna mountain front represents by far the most important and underappreciated seismogenic source in the front of the northern Apennines. Citation: Picotti, V., and F. J. Pazzaglia (2008), A new active tectonic model for the construction of the Northern Apennines mountain front near Bologna (Italy),

The Gulf of Corinth is often considered as a typical example of a more or less simple half graben with major border faults to the south and a flexure of the northern shore. This paper reviews new data, especially subsurface data, from both onshore and offshore, compiled or acquired through the Corinth Rift Laboratory EEC project. This data indicate that (1) the Gulf of Corinth is bordered both north and south by active faults; (2) there is a lot of them, and not only the one bordering the Peloponnese coastline are still active; and (3) distinct opening phases may be recognized on the area. During the first phase, the depocenter was located near the northern shore, whereas during the most recent phase, and only in the centre and the eastern sector, the depocenter moved towards the southern shore. Furthermore, active tectonic, in this western sector, is characterised by a general uplift of the Peloponnese that leads to the formation of new faults, i.e. the Doumena, Aigion and Helike faults and to selective reactivation of older ones such as the Pirgaki fault. We suggest that this current tectonic phase started about 150-120 000 years ago in the Aigion area and about 350 000 years ago eastward (Corinth-city) and that it represents a third opening phase during the growth of the Gulf of Corinth. #

At Iranian longitude, the Arabian plate is moving northward relative to Eurasia ($20 mm yr À1 according to GPS). To the east, this relative motion is accommodated by northward subduction under the E-W Makran emerged accretionary prism. To the west, it is accommodated partly by the Zagros fold-andthrust belt and partly by the Alborz/Kopet Dagh deforming zones further north. This work investigates the NNW striking transition zone that connects Zagros and Makran: the Minab-Zendan fault system. Satellite images, and structural and geomorphic field observations show a distributed deformation pattern covering a wide domain. Five north to NW trending major faults were identified. They exhibit evidence for late Quaternary reverse right-lateral slip, and correspond to two distinct fault systems: the western one transferring the Zagros deformation to the Makran prism, and the eastern one northward transferring the deformation to the Alborz/Kopet Dagh. Tectonic study and fault slip vector analyses indicate that two distinct tectonic regimes have occurred successively since the Miocene within a consistent regional NE trending compression: (1) an upper Miocene to Pliocene tectonic regime characterized by partitioned deformation, between reverse faulting and en echelon folding; (2) a NE trending s 1 axis transpressional regime homogeneously affecting the region since upper Pliocene. The change is contemporaneous with major tectonic reorganization regionally recorded. Therefore this study provides evidence for active deformation that is not localized, but distributed across a wide zone. It accommodates the convergence and transfers it from collision to subduction by transpressional tectonics without any partitioning process in the present-day period.

We present the GIS extension CalHypso to automatically extract multiple hypsometric curves from digital elevation models (DEM). This extension is programmed in Visual Basic 6 and uses the ArcObjects architecture of ArcGIS. It employs a new and easy methodology to extract the hypsometric curve by using the integer data-model properties of ArcGIS and summations algorithms. This provides an optimal integration within the program environment, allowing the representation and comparison of curves directly within the GIS main program. The CalHypso extension can also calculate the main statistics related to the hypsometric curve by applying polynomial fits. We have tested this tool in several basins of the eastern border of the Sierra-Nevada dome in the Betic Cordillera (SE Spain), showing important differences in the north-and southslope hypsometric curves. These variations are probably related to the tectonically controlled drainage evolution of the southern border of Sierra Nevada. An eastward decrease in tectonic-driven erosion is also suggested by the hypsometric curves analyzed.