Alan Linde

Carnegie Institution of Washington, Department of Terrestrial Magnetism, Faculty Member

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Tidal calibration of the Gladwin Tensor Strain Monitor (GTSM) array in Taiwan

To ensure the accuracy and reliability of crustal strain measures, sensors require a thorough cal... more To ensure the accuracy and reliability of crustal strain measures, sensors require a thorough calibration. In Taiwan, the complicated dynamics of surface and subsurface hydrological processes under semi-tropical climate conditions conjugated with the rough surface topography could have impacted strainmeter deployment, pushing the installation conditions astray from the optimal ones. Here, we analyze the complex response of 11 Gladwin Strain Monitor (GTSM) strainmeter type deployed in north and central Taiwan and we propose a novel calibration methodology which relies on waveform modeling of Earth and ocean tidal strain-related deformations. The approach is completely data-driven, starting from a simple calibration framework and progressively adding complexity in the model depending on the quality of the data. However, we show that a simple quasi-isotropic model (3 calibration factors) is generally suitable to resolve the orientation and calibration of 8 instruments out of 11. We als...

Strainmeter measurement at Stromboli Sacks-Evertson borehole, 2019-03-15

Strainmeter measurement at Stromboli Sacks-Evertson borehole, 2019-08-28

Strainmeter measurement at Stromboli Sacks-Evertson borehole, 2019-07-03

Fifteen Years of Continuous High-Resolution Borehole Strainmeter Measurements in Eastern Taiwan: An Overview and Perspectives

GeoHazards

As one of the most sensitive instruments for deformation monitoring in geophysics, borehole strai... more As one of the most sensitive instruments for deformation monitoring in geophysics, borehole strainmeter has the capability to record a large spectrum of tectonic and environmental signals. Sensors are usually deployed near active faults and volcanoes and provide high-resolution continuous recordings of seismic and aseismic signals, hydrological variations (rainfall, groundwater level) and natural hazards (tropical cyclones, landslides, tsunamis). On the occasion of the 50th anniversary of the installation of the first Sacks–Evertson borehole strainmeter, in central Japan, we present an overview of the major scientific contributions and advances enabled by borehole strainmeter measurements in Taiwan since their installation in the mid 2000s. We also propose a set of future research directions that address recent challenges in seismology, hydrology and crustal strain modeling.

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Local perturbations in the western rift of Corinth (Greece) caused by the 2011 Mw 9 Tohoku earthquake: joint observation of strain, water-level and seismic signals

Case 6B: Episodic Aseismic Strain Signal Precursors to the Japan Sea Earthquake of 1983

A source of major error in the digital analysis of World Wide Standard station seismograms

Bulletin of the Seismological Society of America, 1971

A critical requirement in the digitization of analogue seismograms is that the y axis of the digi... more A critical requirement in the digitization of analogue seismograms is that the y axis of the digitizing device be parallel to the recorded direction of swing of the galvanometer. Small misalignment of the seismogram on the digitizing table can produce major errors in the results of Fourier analysis and other digital techniques. In the examples discussed, the direction of the galvanometer swing was not parallel to the recording drum axis (the nominal direction of swing). Fourier spectra and group velocities are presented for cases in which the seismogram is aligned with the x axis of the digitizer: (1) parallel to the trace; (2) normal to the drum axis; (3) correctly aligned, normal to the direction of galvanometer swing. If the alignment is incorrect, the errors in the results are significant at both short and long periods and lead to erroneous geophysical conclusions. The magnitude of the errors increases with both the degree of misalignment and the amplitude of the recorded signal.

Continuous borehole strain in the San Andreas fault zone before, during, and after the 28 June 1992, MW 7.3 Landers, California, earthquake

Bulletin of the Seismological Society of America, 1994

High-precision strain was observed with a borehole dilational strainmeter in the Devil's Punc... more High-precision strain was observed with a borehole dilational strainmeter in the Devil's Punchbowl during the 11:58 UT 28 June 1992 MW 7.3 Landers earthquake and the large Big Bear aftershock (MW 6.3). The strainmeter is installed at a depth of 176 m in the fault zone approximately midway between the surface traces of the San Andreas and Punchbowl faults and is about 100 km from the 85-km-long Landers rupture. We have questioned whether unusual amplified strains indicating precursive slip or high fault compliance occurred on the faults ruptured by the Landers earthquake, or in the San Andreas fault zone before and during the earthquake, whether static offsets for both the Landers and Big Bear earthquakes agree with expectation from geodetic and seismologic models of the ruptures and with observations from a nearby two-color geodimeter network, and whether postseismic behavior indicated continued slip on the Landers rupture or local triggered slip on the San Andreas. We show that...

36 Implications of crustal strain during conventional, slow, and silent earthquakes

International Geophysics, 2002

... If so, the fault model relevant to this process must be inhomogeneous in character to accommo... more

Seismicity Controlled by a Frictional Afterslip During a Small-Magnitude Seismic Sequence (ML < 5) on the Chihshang Fault, Taiwan

Journal of Geophysical Research: Solid Earth, 2018

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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Advances in Understanding Intrusive, Explosive and Effusive Processes as Revealed by the Borehole Dilatometer Network on Mt. Etna Volcano

Frontiers in Earth Science, 2020

For detecting below surface sources of deformation, strain measurements offer a very large advant... more For detecting below surface sources of deformation, strain measurements offer a very large advantage (orders of magnitude) in sensitivity over displacement measurements. On active volcanoes an intriguing open challenge is to measure the strain variations caused by the different types of eruptive activity with the highest possible precision in order to obtain advantages on the clear detecting of phenomena, their modeling and understanding. We present the updated main results obtained from the high precision strain recorded by the borehole dilatometer network on Mt. Etna volcano. The instruments, installed from the end of 2011, detected significant changes during different types of eruptive activity: several lava fountains during 2011-2014; two explosive sequences in 2015 and 2016; moderate effusive activity in 2017 and a dike intrusion in 2018. The strain changes provided powerful diagnostic information on the different ongoing processes, and allowed us to add key information on the different eruptive styles and sources. We also highlight how the recorded signals, with the associated modeling and interpretation, provide a powerful contribution to surveillance requirements on an active volcano. This report demonstrates that the borehole dilatometer network represents a useful tool both for the understanding of the volcano processes and for surveillance needs.

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Testing the Influence of Static and Dynamic Stress Perturbations On the Occurrence of a Shallow, Slow Slip Event in Eastern Taiwan

Journal of Geophysical Research: Solid Earth, 2019

We report the first evidence for the detection of a slow slip event in the Longitudinal Valley, i... more We report the first evidence for the detection of a slow slip event in the Longitudinal Valley, in eastern Taiwan. The slow event, which lasted about 3.5 days, has been detected by borehole strainmeters. It occurred at shallow depths (about 2 to 4 km), either on the Longitudinal Valley Fault or on the Central Range Fault. Here we investigate whether the event occurrence was influenced by transient and periodic stress perturbations, in particular by the June 2013 Mw 6.2 Nantou earthquake, which occurred about 60 km away and 6 days prior to the event. Modeled changes in Coulomb stress in the direction parallel to the geologic slip vector on the fault planes show negative static stress changes (approximately −1.5 to −1 kPa), while maximum dynamic stress changes generated by the surface waves are ranging from 5.5 to 14.5 kPa. We also observe that the slow event initiated during a maximum of Earth and ocean tidal Coulomb stress changes (about 0.8 to 1.5 kPa). Dynamic and static stress pe...

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Triggering of volcanic eruptions

Nature, 1998

Although earthquakes and volcanic eruptions are each manifestations of large-scale tectonic plate... more Although earthquakes and volcanic eruptions are each manifestations of large-scale tectonic plate and mantle motions, it is usually thought that the occurrences of these events are not directly related. There have been some studies, however, in which triggering of volcanic eruptions by earthquakes (remote from the volcano) has been proposed,. The 1992 Landers (southern California) earthquake caused triggered seismicity at very large distances, including the magmatically active Long Valley caldera region which also experienced a significant coincident deformation transient. Motivated by this demonstration of the ability of a distant earthquake to disturb a volcanic system, and the earlier studies of specific cases of eruption triggering, we examine here the historical record of eruptions and earthquakes to see if there are indeed significantly more eruptions immediately following large earthquakes. We find that within a day or two of large earthquakes there are many more eruptions within a range of 750 km than would otherwise be expected. Additionally, it is well known that volcanoes separated by hundreds of kilometres frequently erupt in unison; the characteristics of such eruption pairs are also consistent with the hypothesis that the second eruption is triggered by earthquakes associated with the first.

Calibration for the shear strain of 3-component borehole strainmeters in eastern Taiwan through Earth and ocean tidal waveform modeling

Journal of Geodesy, 2017

We propose an approach for calibrating the horizontal tidal shear components [(differential exten... more We propose an approach for calibrating the horizontal tidal shear components [(differential extension (γ 1) and engineering shear (γ 2)] of two Sacks-Evertson (in Pap Meteorol Geophys 22:195-208, 1971) SES-3 borehole strainmeters installed in the Longitudinal Valley in eastern Taiwan. The method is based on the waveform reconstruction of the Earth and ocean tidal shear signals through linear regressions on strain gauge signals, with variable sensor azimuth. This method allows us to derive the orientation of the sensor without any initial constraints and to calibrate the shear strain components γ 1 and γ 2 against M 2 tidal constituent. The results illustrate the potential of tensor strainmeters for recording horizontal tidal shear strain. Keywords Multi-component borehole strainmeter • Sensor calibration and orientation • Shear strain modeling • Earth and ocean tides • Longitudinal Valley (Taiwan)

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Triggering of Great Earthquakes: Seasonal Variation

Agu Fall Meeting Abstracts, Dec 1, 2005

Strain changes for the 1987 Vatnafj�ll earthquake in south Iceland and possible magmatic triggering

Journal of Geophysical Research, 1999

The Montserrat Soufriere Hills Explosion of March 2004: Magma Geometry and Incompressibility From Borehole Strain Data

Agu Fall Meeting Abstracts, Dec 1, 2008

Vulcanian explosion at Soufri�re Hills Volcano, Montserrat on March 2004 as revealed by strain data

Geophys Res Lett, 2010

Long-Period Volume-Strain Seismogram of the 8 August 1993 Esashi-Oki Earthquake, off Southwest of Hokkaido, Japan and its Source Mechanism

Journal of the Faculty of Science Hokkaido University Series 7 Geophysics, Mar 30, 1998

We present an analysis of the volume-strain data for source parameters of the 8 August 1993 Esash... more We present an analysis of the volume-strain data for source parameters of the 8 August 1993 Esashi-Oki earthquake (MJMA =6.3) which may have been induced by the 12 July 1993 Hokkaido-Nansei-Oki earthquake (MJMA=7.8). Several numerical experiments were carried out to test the hypothesis that the data dependency is attributed to the effect of the source mechanism on the volume-strain seismograms. We used the long-period volume-strain seismogram (DCs; T s; 30 Hz) recorded at the Urakawa Seismological Observatory (KMU) of Hokkaido University, about 230 km southeast of the epicenter of the mainshock. The synthetic volume-strain seismo• grams were calculated using the normal mode theory. The experiments provided the best fitted source parameters: (strike, dip, rake) = (196°, 5T, 90°) with the seismic moment Mo=2.8 x 10 18 Nm (Mw=6.2). This solution is similar to the CMT solution obtained by using the worldwide long-period seismograms, of which mechanism is characterized by steeper-dipping and north-south-directing nodal planes. This result is supported by the distribution of aftershoks. Such a volume-strain seismo• gram may provide not only an estimation of the seismic moment but also a refinement

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Alan Linde

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