I am a geologist with research interests in the broad field of tectonic geomorphology, working on earthquakes, active faults, river incision, exhumation and erosion.
Modeling repeated coseismic slip to identify and characterize individual earthquakes from geomorphic offsets on strike-slip faults
Earth and Planetary Science Letters
Abstract Coseismic slip distributions of repeated earthquakes are important data used to forecast... more Abstract Coseismic slip distributions of repeated earthquakes are important data used to forecast magnitude and recurrence characteristics of future earthquakes. Many studies infer coseismic slip of past individual paleoearthquakes from frequency histograms of geomorphic offsets. Such histograms, often expressed as a COPD (cumulative offset probability distribution), commonly show multiple peaks with similar displacements, which are interpreted to be incremental slip associated with successive paleoearthquakes. However, assumptions in linking COPD peaks to individual earthquakes have not been fully explored. Here, we combine statistical modeling with global historical coseismic surface rupture data to evaluate the conditions required for the approach. The results show that only coseismic slip with low variability allow more than one event identification; for example, even low CoVs (coefficient of offset variation) of 0.25 and 0.35 permit identification of only 2 to 3 events. In contrast, the mean CoV value for all historical ruptures is 0.58 to 0.66. Furthermore, interpreting the first COPD peak as a single-event slip distribution could result in artificially low variation and flatter distribution of offset than observed in historical earthquakes. This study cautions that robust COPD interpretation on large strike-slip faults requires low offset variability, a sufficient number of offset measurements, and additional constraints like historical coseismic slip data or paleoseismic event sequence data.
Enhanced Quaternary Exhumation in the Central Three Rivers Region, Southeastern Tibet
Frontiers in Earth Science
The roles of tectonics and climate in the global increased erosion rates during the Quaternary ha... more The roles of tectonics and climate in the global increased erosion rates during the Quaternary have been the subject of active debate. The Three Rivers Region, strongly influenced by continental convergence between India and Eurasia and change in Asian monsoon climate, is an ideal place to study the interactions between tectonics and surface processes. Here we report new apatite (U-Th)/He data from an elevation transect that reveal a phase of rapid exhumation since ∼2.6 Ma in the Dulong batholith in the central Three Rivers Region, southeastern Tibetan Plateau. Based on stream profile analysis and compiled thermochronological data in the region, we demonstrate that the tectonic uplift caused by the high-strain at the corner of Indian-Eurasia convergence is responsible for the enhanced exhumation in the central Three Rivers Region in the Quaternary. Our new results highlight that the continuous plate convergence towards the plateau interior has dominated the uplift and deformation in...
Landslides of the 1920 Haiyuan earthquake, northern China
Landslides
The great M ~ 8 1920 Haiyuan earthquake (HYEQ) was one of the largest and most deadly earthquakes... more The great M ~ 8 1920 Haiyuan earthquake (HYEQ) was one of the largest and most deadly earthquakes in China in the last century, with ~ 234,000 deaths. The earthquake occurred within the Loess Plateau of northern China, where Quaternary loess deposits form a distinctive blanket across the landscape. Large regions of this loess cover experienced co-seismic landslides. Based on an analysis of the original disaster reports, field surveys, and satellite image interpretation, we have compiled the shaking effects of the earthquake, including the distribution of landslides, fatalities, and structural damage. Landslides triggered by the HYEQ (n > 7,000) are concentrated south of the Haiyuan fault, in a region that has both thick loess cover and long-term relief generated by the drainage network. This distribution is spatially separated from landslides triggered by other earthquakes. We find that in contrast to previous studies, the most important factor in the severe death toll of the HYEQ was the collapse of housing by ground shaking, including collapse of loess house-caves. Landslides were a secondary factor; although up to 32,000 deaths occurred in areas with intense landsliding. Based on the revised distribution pattern of landslides and damage (e.g., house collapses), we suggest that the isoseismal intensity IX line extends south of previous locations. We have also identified 126 dammed lakes created by co-seismic landslides, which form major modifications of this semi-arid landscape. The research methods in this paper, combining historical review, satellite image interpretation, and field validation of landslides, can be used as a reference for studies of other areas affected by historical earthquakes and co-seismic landslides, elsewhere in the Loess Plateau and beyond.
Paleoseismologic record of earthquakes along the Wuzunxiaoer section of the Altyn Tagh fault and its implication for cascade rupture behavior
Science China Earth Sciences
The Altyn Tagh fault is one of the few great active strike-slip faults in the world. The recurren... more The Altyn Tagh fault is one of the few great active strike-slip faults in the world. The recurrence characteristics of paleoearthquakes on this fault are still poorly understood due to the lack of paleoseismic records recorded in high-resolution strata. We document a paleoseismic record in a pull-apart basin along the Wuzunxiaoer section of the central Altyn Tagh fault. The high-resolution strata recorded abundant seismic deformations and their sedimentary responses. Four earthquakes are identified based on event evidence in the form of open fissures, thickened strata, angular unconformities, and folds. The occurrence times of the four events were constrained using radiocarbon dating. Event W1 occurred at AD1220-1773, events W2 and W3 occurred between 407 and 215BC, and event W4 occurred slightly earlier at 1608-1462BC, indicating clustered recurrence characteristics. A comparison of the earthquake records along the Wuzunxiaoer section with other records along the Xorkoli section suggests that both sections ruptured during the most recent event.
High-resolution topographic or imagery data effectively reveal geomorphic offsets along faults th... more High-resolution topographic or imagery data effectively reveal geomorphic offsets along faults that can be used to deduce slipper event of recurrent rupture events. Documentation of patterns of geomorphic offsets is scarce on faults that undergo both creep and coseismic rupture. In this paper, we used newly acquired high-resolution light detection and ranging (LiDAR) data to compile geomorphic offsets along the Laohu Shan section of the Haiyuan fault, in the northern Tibetan Plateau, where interferometric synthetic aperture radar (InSAR) data suggest creep presently occurs over a 35-km-long stretch at a rate comparable to the long-term geological slip rate, despite evidence for past coseismic fault rupture. Numerous offset gullies identified using the LiDAR data yield a range of offsets from less than 2 m up to 50 m. These offsets have well-separated probability density peaks at 2-3 m, ~7 m, and ~14 m, with increments of 2-3 m, 4-6 m, and 5-7 m. The sequence of paleoseismic events along the Laohu Shan section indicates that the gullies with offsets of 2-3 m are likely related to surface rupture of the historical 1888 Jingtai earthquake, plus subsequent creep. Offset increments of 4-6 m and 5-7 m may represent coseismic slip in past paleoseismic events plus creep during the interseismic period. The creeping Laohu Shan section preserves numerous discrete cumulative offsets, with an offset clustering pattern indistinguishable from that on a locked fault with recurrent earthquake ruptures. Association of offset increments with known paleoseismic events yields a slip rate of 3-5 mm/yr during the past 200 years, roughly similar to the ~5 mm/yr creep rate. If the ratio of surface creep rate to the total fault slip rate has been continuous, then seismic moment release by brittle ruptures, and thus seismic hazard, would be much reduced on the Laohu Shan section of the Haiyuan fault. Alternatively, the current high creep rate may be a transient phenomenon, perhaps after slip following the 2000 Jingtai Mw 5.6 earthquake or in response to the adjacent 1920 M ~8 Haiyuan earthquake rupture that terminated immediately to the east.
Emplacement depth of the Shidao granitic complex and the rapid exhumation of the Sulu ultrahigh pressure rocks: New constraints on the mechanisms for rapid exhumation
In their Comment, Zeitler et al. do not challenge our results or interpretation. Our study does n... more In their Comment, Zeitler et al. do not challenge our results or interpretation. Our study does not disprove coupling between tectonic uplift and erosion but suggests that this coupling cannot be the sole explanation of rapid uplift in the Himalayan syntaxes.
大地震破裂大多由横向构造（如阶区、弯曲和分叉）所分割的多个段落组成．２００８年５·１２汶川地震破裂沿北东走向上穿过了多个横向构造部位，特别在震中北东４５ｋｍ 的位置，小鱼洞断层、北川断层和彭灌断... more 大地震破裂大多由横向构造（如阶区、弯曲和分叉）所分割的多个段落组成．２００８年５·１２汶川地震破裂沿北东走向上穿过了多个横向构造部位，特别在震中北东４５ｋｍ 的位置，小鱼洞断层、北川断层和彭灌断层三者之间呈现复杂的断裂切割相交关系．复杂断层几何结构对破裂的扩展是有抑制还是促进的作用？在相交的断裂段之间是否存在最优的破裂顺序？本文以库仑应力分析为手段，探讨在汶川同震破裂初始３０ｓ内，破裂在多分支断裂中选择扩展路径时的可能应力相互作用．库仑应力分析显示：如果北川断层先发生破裂，其滑动对小鱼洞断层和彭灌断层均产生强烈负应力的抑制作用，而彭灌断层的滑动却反而对小鱼洞断层和北川断层浅部有强烈正应力的促进作用．因此，从准静态应力分析角度，彭灌断层先于北川断层发生破裂的可能性较大，这一破裂顺序与小鱼洞断层参与同震破裂过程的事实相符．此外，小鱼洞断层在链接北川和彭灌断层的同震位移中可能起到桥梁作用，但非静态应力的影响．横向构造在逆冲型地震破裂扩展过程中起到的牵引作用使得逆冲型地震破裂能够比走滑型地震跨越更宽的阶区．横向构造是逆冲断裂带内广泛发育的构成单元，因此在地震危险性分析的最大潜在震级测算中应该考虑其作用．
Transpression along the Altyn Tagh fault and terminations of large ruptures at the Aksay restraining bend: results from numerical modeling and the observed earthquake record
Field evidence and numerical modeling suggest that the Aksay restraining double-bend of the Altyn... more Field evidence and numerical modeling suggest that the Aksay restraining double-bend of the Altyn Tagh fault (ATF) may serve as a barrier to great earthquakes by terminating major strike-slip ruptures. The Altyn Tagh fault generally defines the northwestern margin of the Tibet-Qinghai plateau, accommodating transpressive northeastward motion of the plateau with respect to the Tarim block and stable Eurasia to its north and west. Transpression is enhanced at major restraining double-bends along the ATF (including the Sulamu Tagh, Akato Tagh, and Aksay bends). Contemporary activity of two parallel fault strands within the Aksay bend and stepover (see figure) requires separate rupture of each fault, implying that the bend stops incoming ruptures on either fault. Geomorphic observations indicate that slip is transferred between the northern and southern strands of the ATF at the Aksay bend, and multi-cycle numerical rupture models of the system suggest that this tradeoff in slip is mani...
Earthquakes of moderate magnitude recorded at the Salt Lake paleoseimic site on the Haiyuan Fault, China
ABSTRACT The active left-lateral Haiyuan fault is one of the major continental strike-slip faults... more ABSTRACT The active left-lateral Haiyuan fault is one of the major continental strike-slip faults in the Tibetan Plateau. The last large earthquake occurred on the fault is the great 1920 M~8 Haiyuan earthquake with a 230-km-long surface rupture and maximum surface slip of 11 m (Zhang et al., 1987). Much less known is its earthquake recurrence behavior. We present preliminary results on a paleoseismic study at the Salt Lake site, at a shortcut pull-apart basin, within the section that broke in 1920. 3D excavation at the site exposed 7 m of fine-grained and layered stratigraphy and ample evidence of 6-7 paleoseismic events. AMS dating of charcoal fragments constrains that the events occurred during the past 3600 years. Of these, the youngest 3-4 events are recorded in the top 2.5m section of distinctive thinly-layered stratigraphy of alternating reddish well-sorted granule sand and light gray silty fine sand. The section has been deposited since ~1550 A.D., suggesting 3-4 events occurred during the past 400 years, and an average recurrence interval of less than 150 years, surprisingly short for the Haiyuan fault, with a slip rate of arguably ~10 mm/yr or less. A comparison of paleoseismic with historical earthquake record is possible for the Haiyuan area, a region with written accounts of earthquake effects dated back to 1000 A.D.. Between 1600 A.D. and present, each of the four paleoseismic events can be correlated to one historically recorded event, within the uncertainties of paleoseismic age ranges. Nonetheless, these events are definitely not 1920-type large earthquakes, because their shaking effects were only recorded locally, rather than regionally. More and more studies show that M5 to 6 events are capable of causing ground deformation. Our results indicate that it can be misleading to simply use the time between consecutive events as the recurrence interval at a single paleoseismic site, without information of event size. Mixed events of different magnitudes in the record will give a false sense of short recurrence intervals for the implied large characteristic magnitude for recurring events.
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Papers by Jing Liu-Zeng