https://seismica.library.mcgill.ca/issue/feed Seismica 2024-11-06T12:43:35-05:00 Seismica Editorial Team info@seismica.org Open Journal Systems <p>Seismica is a community-driven, <em>Diamond Open Access</em> journal publishing peer-reviewed research in seismology and earthquake science. <em>Diamond Open Access</em> journals are free for all to read, without subscriptions, and do not charge article processing fees to authors. Seismica publishes one volume with two regular issues and one or more special issue per year. </p> <p>Seismica has been open for submission since July 2022. You can read more about the motivation and philosophy that drove founding Seismica in <a href="https://seismica.library.mcgill.ca/announcement/view/12">our first editorial</a>, and get an overview of our workflow in our <a href="https://seismica.library.mcgill.ca/article/view/1091">second editorial</a>. Thank you to all the members of the Seismica community who contributed to these editorials!</p> <p><strong>[November 2023] Seismica is soliciting submissions for a special issue, "<a href="https://seismica.library.mcgill.ca/announcement/view/17">The Cascadia Subduction Zone: Grand Challenges and Research Frontiers</a>" For more information on submitting a paper, see the <a href="https://seismica.library.mcgill.ca/announcement/view/17">issue announcement</a>.</strong></p> https://seismica.library.mcgill.ca/article/view/1152 Modeling ground motions and crustal deformation from tsunami earthquakes: Rupture parameter constraints from the 2010 Mentawai event 2024-07-22T11:37:31-04:00 Tara Nye tnye@uoregon.edu Valerie Sahakian vjs@uoregon.edu Diego Melgar dmelgarm@uoregon.edu <p>We use a combination of near-field simulated and observational data to constrain the rise time, rupture velocity, and high frequency stress parameter for the 2010 M7.8 Mentawai tsunami earthquake. Tsunami earthquakes, which are shallow-rupturing events generating exceptionally large seafloor displacements, are challenging for current tsunami early warning systems. A combination of near-field high-rate GNSS and seismic data can be used for early-discrimination, but the dearth of data from these events limits testing of such an implementation in a real-time scenario. In lieu of near-field data, models with realistic rupture physics can be leveraged to improve local tsunami warning. We develop recommendations for such parameters based on observations of near-field data from the 2010 M7.8 Mentawai earthquake. We find that rise time and rupture velocity covary, and that rise time–rupture velocity combinations ranging from 5.4 s–1.23 km/s to 12 s–1.6 km/s adequately model the long duration of the Mentawai event. We find that a stress parameter of 1.43 MPa best models the high frequency deficiency. We present equations which can be used to determine reasonable parameter values for simulating tsunami earthquakes, and we find that simulated data generated with the recommended parameters capture defining characteristics of tsunami earthquakes.</p> 2024-09-28T00:00:00-04:00 Copyright (c) 2024 Tara Nye, Valerie J. Sahakaian, Diego Melgar https://seismica.library.mcgill.ca/article/view/1337 Microseismicity at the Time of a Large Creep Event on the Calaveras Fault is Unresponsive to Stress Changes 2024-10-02T10:33:37-04:00 Litong Huang lhuang56@ucsc.edu Susan Schwartz syschwar@ucsc.edu Emily Brodsky brodsky@ucsc.edu <p>The potential relationship between surface creep and deeper geological processes is unclear, even on one of the world’s best-studied faults. From June to August 2021, a large creep event with surface slip of more than 16 mm was recorded on the Calaveras fault in California, part of the San Andreas fault system. This event initially appeared to be accompanied by along-fault migration of seismicity, suggesting it penetrated to depth. Other studies have suggested that surface creep events are likely a shallow feature, unrelated to deep seismicity. To provide more detail on the relationship between earthquakes, surface creep, and potential aseismic slip at seismogenic depth, we tripled the number of earthquakes in the Northern California Earthquake Catalog in the region of the creep event for all of 2021. This was accomplished by implementing earthquake detection techniques based on both template matching (EQCorrscan) and AI-based automatic earthquake phase picking (PhaseNet). After manual inspection, the detected earthquakes were first located using Hypoinverse and subsequently relocated via GrowClust. Our enhanced catalog indicates that the spatiotemporal pattern of earthquakes here is not strongly influenced by the creep event and is better explained by structural heterogeneity than transient stress changes, indicating a decoupling of seismicity rate and surficial creep on this major fault.</p> 2024-10-02T00:00:00-04:00 Copyright (c) 2024 Litong Huang, Susan Y Schwartz, Emily E Brodsky https://seismica.library.mcgill.ca/article/view/1351 Heterogeneous high frequency seismic radiation from complex ruptures 2024-09-17T12:33:52-04:00 Sara Cebry sarabethleach@gmail.com Gregory McLaskey gcm8@cornell.edu <p>Fault geometric heterogeneities such as roughness, stepovers, or other irregularities are known to affect the spectra of radiated waves during an earthquake. To investigate the effect of normal stress heterogeneity on radiated spectra, we utilized a poly(methyl methacrylate) (PMMA) laboratory fault with a single, localized bump. By varying the normal stress on the bump and the fault-average normal stress, we produced earthquake-like ruptures that ranged from smooth, continuous ruptures to complex ruptures with variable rupture propagation velocity, slip distribution, and stress drop. High prominence bumps produced complex events that radiated more high frequency energy, relative to low frequency energy, than continuous events without a bump. In complex ruptures, the high frequency energy showed significant spatial variation correlated with heterogeneous peak slip rate and maximum local stress drop caused by the bump. Continuous ruptures emitted spatially uniform bursts of high frequency energy. Near-field peak ground acceleration (PGA) measurements of complex ruptures show nearly an order-of-magnitude higher PGA near the bump than elsewhere. We propose that for natural faults, geometric heterogeneities may be a plausible explanation for commonly observed order-of-magnitude variations in near-fault PGA.</p> 2024-09-17T00:00:00-04:00 Copyright (c) 2024 Sara Cebry, Greg McLaskey https://seismica.library.mcgill.ca/article/view/1146 Performance of synthetic DAS as a function of array geometry 2024-10-31T09:57:13-04:00 Thomas Luckie twlucki@sandia.gov Robert Porritt rwporri@sandia.gov <p class="Abstracttext">Distributed Acoustic Sensing (DAS) <span class="normaltextrun">can record acoustic wavefields at high sampling rates and with dense spatial resolution difficult to achieve with seismometers. Using optical scattering induced by cable deformation, DAS </span><span class="advancedproofingissue">can</span><span class="normaltextrun"> record strain fields with ones of meters spatial resolution. However, many experiments utilizing DAS have relied on unused, dark telecommunication fibers. As a result, the geophysical community has not fully explored DAS survey parameters to characterize the ideal array design. </span><span class="contextualspellingandgrammarerror">This limits</span><span class="normaltextrun"> our understanding of guiding principles in array design to deploy DAS effectively and efficiently in the field.</span> <span class="normaltextrun">A better quantitative understanding of DAS array behavior can help improve the quality of the data recorded by guiding the DAS array design.</span> <span class="normaltextrun">Here we use array response functions as well as beamforming and </span><span class="spellingerror">back-projection</span><span class="normaltextrun"> results from forward modelling calculations to assess the performance of varying DAS array geometries to record regional and local sources.</span> <span class="normaltextrun">A regular heptagon DAS array demonstrated improved capabilities for recording regional sources over segmented linear arrays, with potential improvements in recording and locating local sources.</span> <span class="normaltextrun">These results reveal DAS array performance as a function of geometry and can guide future DAS deployments.</span><span class="eop">&nbsp;</span></p> 2024-10-31T00:00:00-04:00 Copyright (c) 2024 Thomas Luckie, Robert Porritt https://seismica.library.mcgill.ca/article/view/1165 An exploration of potentially reversible controls on millennial-scale variations in the slip rate of seismogenic faults: Linking structural observations with variable earthquake recurrence patterns 2024-01-19T05:12:13-05:00 Tarryn Cawood cawood.tk@gmail.com James Dolan dolan@usc.edu <p>Paleoseismic studies show that faults within a fault system may trade off slip over time, with mechanically complementary faults displaying alternating fast- and slow periods. Each of these periods spans multiple seismic cycles, and typically involves ~20-25m of slip. This suggests that the relative strength (or tendency to slip) of individual faults varies, over time and displacement scales larger than those of individual seismic cycles. The mechanisms responsible for these strength variations must: affect rocks in the strongest portion of the fault (the brittle-ductile transition) as this likely controls the overall slip rate of the fault; be reversible (or able to be counteracted) on a cyclical basis; provide a negative feedback that operates to change the fault from its current state; and have a measurable effect on fault strength over a time or length scale that corresponds to the observed fast and slow periods of fault slip. In this paper, we systematically explore 19 potentially weakening and 11 potential strengthening mechanisms and evaluate them in light of these criteria. This analysis reveals a relatively small subset of mechanisms that could account for the observed behavior, leading us to suggest a possible model for fault strength evolution.</p> 2024-07-22T00:00:00-04:00 Copyright (c) 2024 © His Majesty the King in Right of Canada, as represented by the Minister of Natural Resources, 2023 https://seismica.library.mcgill.ca/article/view/1206 Statistical distribution of static stress resolved onto geometrically-rough faults 2024-05-03T02:16:07-04:00 Jeremy Maurer jmaurer@mst.edu <p>The in-situ stress state within fault zones is technically challenging to characterize, requiring the use of indirect methods to estimate. Most work to date has focused on understanding average properties of resolved stress on faults, but fault non-planarity should induce spatial variations in resolved static stress on a single fault. Assuming a particular stochastic model for fault geometry (band-limited fractal) gives an approximate analytic solution for the probability density function (PDF) on fault stress that depends on the mean fault orientation, mean stress ratio, and roughness level. The mean stress is shown to be equal to the planar fault value, while deviations are described by substituting a second-order polynomial expansion of the stress ratio into the inverse distribution on fault slope. The result is an analytical expression for the PDF of shear-to-normal stress ratio on 2-D rough faults in a uniform background stress field. Two end-member distributions exist, one approximately Gaussian when all points on the fault are well away from failure, and one reverse exponential, which occurs when the mean stress ratio approaches the peak. For the range of roughness values expected to apply to crustal faults, stress deviations due to geometry can reach nearly 100% of the background stress level. Consideration of such a distribution of stress on faults suggests that geometric roughness and the resulting stress deviations may play a key role in controlling earthquake behavior.</p> 2024-07-23T00:00:00-04:00 Copyright (c) 2024 Jeremy Maurer https://seismica.library.mcgill.ca/article/view/1344 An Open Source Hydroacoustic Benchmarking Framework for Geophonic Signal Detection 2024-05-03T02:30:03-04:00 Pierre-Yves Raumer pierre-yves.raumer@univ-brest.fr Sara Bazin sara.bazin@univ-brest.fr Dorian Cazau dorian.cazau@ensta-bretagne.fr Vaibhav Vijay Ingale vaibhavvijay.ingale@univ-brest.fr Jean-Yves Royer jean-yves.royer@univ-brest.fr Aude Lavayssière aude.lavayssiere@gmail.com <p>Passive hydroacoustic studies have underscored the efficiency and relevance of deploying autonomous hydrophones for the surveillance of underwater geophony. In particular, monitoring networks have been deployed for detecting SOFAR-propagating hydroacoustic waves generated by seismic events and locating their sources. The technique has been extended to study other hydroacoustic signals, such as P-waves from teleseismic events or impulsive waves generated by sea water-lava interactions. A significant challenge in this endeavor lies in the time required for the manual detection and annotation of these signals in long-term records. To address this issue, we tested the feasibility of implementing automated algorithms based on machine learning to detect and identify these various signals, and obtained satisfying classification and time picking accuracies. We incorporated those models in a benchmarking framework, proposing a training dataset, two evaluation datasets, two tasks to solve and the evaluations of the mentionned models on them. The goal of this framework is to foster the development of new models in the community, as it gives a clear way to evaluate them.</p> 2024-10-14T00:00:00-04:00 Copyright (c) 2024 Pierre-Yves Raumer, Sara Bazin, Dorian Cazau, Vaibhav Vijay Ingale, Jean-Yves Royer, Aude Lavayssière https://seismica.library.mcgill.ca/article/view/1382 A model of the earthquake cycle along the Gofar oceanic transform faults 2024-10-16T17:03:49-04:00 Meng (Matt) Wei matt-wei@uri.edu Lingchao He helingchao@uri.edu Bridget Smith-Konter brkonter@hawaii.edu <p>The Gofar oceanic transform fault at the East Pacific Rise has one of the best seismic cycles recorded by modern instruments. The timing, location, and magnitude of major earthquakes (M<span class="annotation subscript" data-id="subscript_1">w</span>&gt;5.5) have been well constrained by data from global seismic networks for the past 30 years. The earthquake interval is short, about 3-5 years. Several segments have already experienced 5 cycles since 1995, when the seismic network was good enough for surface wave relocation. Two ocean bottom seismometer deployments (2008-2009, 2021-2023) also provide constraints on the seismic properties on the fault. This makes Gofar an ideal place to study earthquake cycles. Here, we developed a model for the seismic cycle along the Gofar transform fault using a semi-analytical approach for rapidly calculating 3D time-dependent deformation and stress caused by screw dislocations embedded within an elastic layer overlying a Maxwell viscoelastic half-space. The 160-km long fault is divided into three major segments with six asperities. Our model simulates the earthquake pattern on this fault for the past 30 years. Most of the time, each asperity ruptured as a large earthquake every 3-5 years. Most segments have a nearly constant Coulomb stress threshold of 2-3 MPa, providing optimal conditions for the forecasting of future earthquakes along Gofar. For three cases that deviated from this simple regular pattern, a large earthquake occurred with a centroid location between two asperities. This is likely due to concurrent rupture that involved both asperities. We also modeled surface deformation with different elastic layer thicknesses and mantle viscosities. Even though most deformation is in the horizontal direction, the difference in both horizontal and vertical directions between models can be as large as a few centimeters per year. Several seafloor geodesy methods can be used to differentiate between models, and seafloor pressure might be the most appropriate one at this remote location.</p> 2024-11-06T00:00:00-05:00 Copyright (c) 2024 Meng (Matt) Wei, Lingchao He, Bridget Smith-Konter https://seismica.library.mcgill.ca/article/view/1094 The Pattern of Earthquake Magnitude Clustering Based on Interevent Distance and Time 2024-08-29T09:10:55-04:00 Derreck Gossett Gossett gossetd@miamioh.edu Michael Brudzinski brudzimr@miamioh.edu Xiong Qiquan qxiong26@wisc.edu Jesse Hampton jesse.hampton@wisc.edu <p>The clustering of earthquake magnitudes is poorly understood compared to spatial and temporal clustering. Better understanding of correlations between earthquake magnitudes could provide insight into the mechanisms of earthquake rupture and fault interactions, and improve earthquake forecasting models. In this study we present a novel method of examining how seismic magnitude clustering occurs beyond the next event in the catalog and evolves with time and space between earthquake events. We first evaluate the clustering signature over time and space using double-difference located catalogs from Southern and Northern California. The strength of magnitude clustering appears to decay linearly with distance between events and logarithmically with time. The signature persists for longer distances (more than 50km) and times (several days) than previously thought, indicating that magnitude clustering is not driven solely by repeated rupture of an identical fault patch or Omori aftershock processes. The decay patterns occur in all magnitude ranges of the catalog and are demonstrated across multiple methodologies of study. These patterns are also shown to be present in laboratory rock fracture catalogs but absent in ETAS synthetic catalogs. Incorporating magnitude clustering decay patterns into earthquake forecasting models such as ETAS could improve their accuracy.</p> 2024-08-29T00:00:00-04:00 Copyright (c) 2024 Derreck Gossett, Michael R. Brudzinski, Qiquan Xiong, Jesse C. Hampton https://seismica.library.mcgill.ca/article/view/1153 Spatiotemporal Variability of Fin Whale and Blue Whale Calls Detected by Land Seismometers Along the Lower St. Lawrence Seaway 2024-09-16T09:31:44-04:00 Eva Goblot eva.goblot@dal.ca Yajing Liu yajing.liu@mcgill.ca Alexandre Plourde ap.plourde@gmail.com Pierre Cauchy pierre_cauchy@uqar.ca Jeanne Mérindol jeanne.theuriot@gmail.com Coralie Bernier coralie.bernier@hotmail.com Ge Li ge.li@mila.quebec Basile Roth basileroth.75@gmail.com <div class="page" title="Page 1"> <div class="layoutArea"> <div class="column"> <p>The Lower St. Lawrence Seaway (LSLS) is critical to Canada’s economy both as part of a major marine shipping corridor and a site of intensive fishing. Every year, fin whales and blue whales frequent the LSLS feeding ground. Understanding the mechanisms driving whale habitat usage is key for making informed decisions on shipping and fishing, reducing whale collision risks and mitigating noise pollution. We detect whales in the LSLS with land seismometers by using a method that relies on the intervals of the regularly repeating low frequency calls. The resulting catalogue contains 14,076 fin whale detections and 3,739 blue whale detections between February 2020 and January 2022. These detections follow the overall pattern of hydrophones, with most detections from fall to early winter in the Estuary and until mid-winter/spring in the Gulf. High detection rates in the Northwest Gulf throughout the winter months demonstrate that this region is potentially utilized year-round. This labelled catalogue may be suitable for developing a deep learning-based whale call detection algorithm. Making use of seismometers and deep learning can increase whale monitoring coverage within the LSLS and elsewhere.</p> </div> </div> </div> 2024-09-16T00:00:00-04:00 Copyright (c) 2024 Eva Goblot, Yajing Liu, Alexandre Plourde, Pierre Cauchy, Jeanne Mérindol, Coralie Bernier, Ge Li, Basile Roth https://seismica.library.mcgill.ca/article/view/1202 Refined Holocene Slip Rate for the Western and Central Segments of the Garlock Fault: Record of Alternating Millennial-Scale Periods of Fast and Slow Fault Slip 2024-07-05T08:08:17-04:00 Dannielle Fougere dfougere@usc.edu James Dolan dolan@usc.edu Edward Rhodes Ed.Rhodes@sheffield.ac.uk Sally McGill SMcGill@csusb.edu <p>We use lidar- and field-based mapping coupled with single-grain infrared-stimulated luminescence dating to constrain three new slip rate estimates from the western and central segments of the Garlock fault in southern California, revealing a more complete picture of incremental slip rate in time and space for this major plate-boundary fault. These new rates reinforce and refine previous evidence showing that the Garlock fault experiences significant temporal variations in slip rates that span multiple earthquake cycles, with multi-millennial periods of very fast (13-14 mm/yr) early and late Holocene slip separated by a mid-Holocene period of slow slip (3 mm/yr). Similar ca. 8 ka slip rates for the central Garlock fault of 8.8 ± 1.0 mm/yr and 8.2 +1.0/-0.8 mm/yr for the western Garlock fault demonstrate that the fault has slipped at a faster long-term average rate than suggested by previous studies. These fast rates are consistent with kinematic models in which the western and central Garlock fault segments are driven primarily by lateral extrusion associated with N-S contractional shortening, with additional slip driven by WNW-ENE Basin and Range extension north of the fault and minor rotation of the Garlock within the N-S zone of dextral ECSZ shear.</p> 2024-07-05T00:00:00-04:00 Copyright (c) 2024 Dannielle Fougere, James Dolan, Edward Rhodes, Sally McGill https://seismica.library.mcgill.ca/article/view/1354 Imaging microearthquake rupture processes using a dense array in Oklahoma 2024-09-03T06:31:30-04:00 Harrison Burnett hburnett@ucsd.edu Wenyuan Fan wenyuanfan@ucsd.edu <p>Both large and small earthquakes rupture in complex ways. However, microearthquakes are often simplified as point sources and their rupture properties are challenging to resolve. We leverage seismic wavefields recorded by a dense array in Oklahoma to image microearthquake rupture processes. We construct machine-learning enabled catalogs and identify four spatially disconnected seismic clusters. These clusters likely delineate near-vertical strike-slip faults. We develop a new approach to use the maximum absolute SH-wave amplitude distributions (S-wave wavefields) to compare microearthquake rupture processes. We focus on one cluster with earthquakes located beneath the dense array and have a local magnitude range of -1.3 to 2.3. The S-wave wavefields of single earthquakes are generally coherent but differ slightly between the low-frequency (&lt;12 Hz) and high-frequency (&gt;12 Hz) bands. The S-wave wavefields are coherent between different earthquakes at low frequencies with average correlation coefficients greater than 0.95. However, the wavefield coherence decreases with increasing frequency for different earthquakes. This reduced coherence is likely due to the rupture differences among individual earthquakes. Our results suggest that earthquake slip of the microearthquakes dominates the radiated S-wave wavefields at higher frequencies. Our method suggests a new direction in resolving small earthquake source attributes using dense seismic arrays without assuming a rupture model.</p> 2024-09-03T00:00:00-04:00 Copyright (c) 2024 Harrison Burnett, Wenyuan Fan https://seismica.library.mcgill.ca/article/view/1151 Seismic site conditions of RESNOM network 2024-10-22T17:56:12-04:00 Lenin Ávila-Barrientos lenavila@cicese.mx Luis A. Yegres-Herrera yegres@cicese.mx Hortencia Flores-Estrella hortencia.flores@gtn-online.de M. Alejandra Nuñez-Leal anunez@cicese.mx Hector Gonzalez-Huizar hgonzalez@cicese.mx <p>The Northwest Seismic Network of Mexico (RESNOM) is operated by personnel from the Center for Scientific Research and Higher Education of Ensenada, Baja California (CICESE), which supervises station installation, improvement, and maintenance. We employed seismic noise and the Horizontal to Vertical Spectral Ratio (HVSR) method to determine, for each station, the following site condition parameters: the depth of the rock layer (<em>H<sub>eng_bed</sub></em>), and the geotechnical parameter <em>V<sub>S30</sub></em>, obtained from 1D shear wave velocity models. Other parameters as the fundamental frequency (<em>f<sub>0</sub></em>) and the average amplitude at the fundamental frequency (<em>A<sub>0</sub></em>) were also estimated. Our results show clear differences between the values obtained for the Mexicali Valley and the Peninsular ranges regions. The <em>V<sub>S30</sub> </em>obtained for stations of the Mexicali Valley region falls in the range from 173 m/s to 535 m/s, while for the Peninsular Ranges region is between 213 m/s and 958 m/s. Regarding the <em>H<sub>eng_bed</sub></em> parameter, the values are similar between both regions, from 23 m to 850 m for the Peninsular and from 42 m to 926 m for the Mexicali Valley. Additionally, from the <em>V<sub>S30</sub></em> values, we propose the site classification according to the U.S. National Earthquake Hazards Reduction Program (NEHRP).</p> 2024-10-22T00:00:00-04:00 Copyright (c) 2024 Lenin Ávila-Barrientos, Luis A. Yegres-Herrera, Hortencia Flores-Estrella, M. Alejandra Nuñez-Leal, Hector Gonzalez-Huizar https://seismica.library.mcgill.ca/article/view/1310 Along-strike extent of earthquakes on multi-segment reverse faults; insights from the Nevis-Cardrona Fault, Aotearoa New Zealand 2024-10-31T10:17:02-04:00 Jack Williams jack.williams@otago.ac.nz Mark Stirling mark.stirling@otago.ac.nz Robert Langridge R.Langridge@gns.cri.nz Govinda Niroula nirgo392@student.otago.ac.nz Ashleigh Vause vauas584@student.otago.ac.nz James Stewart jstewart@geosolve.co.nz Andy Nicol andy.nicol@canterbury.ac.nz Ninghseng Wang ningsheng.wang@vuw.ac.nz <p>Evaluating fault segmentation is important for our understanding of seismic hazard assessment and fault growth. However, it is still unclear what controls if reverse fault earthquakes will rupture across segment boundaries. Here, we combine fault mapping and trench data from the low slip rate (0.04-0.15 mm/yr) multi-segment Nevis-Cardrona Fault (NCF) in the South Island of Aotearoa New Zealand to assess if it has ruptured in single or multi-segment earthquakes during the late Quaternary. Two new trenches on its Nevis segment provide stratigraphic evidence for two surface rupturing earthquakes, which through Optically Stimulated Luminscence dating and OxCal modelling, are constrained to have occurred at 28.9 +12.9 -9.1 ka and 12.8 ± 4.9 ka. The most recent timing is only weakly correlated to surface rupture timings from two trenches along the NCF's NW Cardrona segment. Furthermore, the 2 ± 1 m Nevis segment single event displacements we estimate would be unusually low for a ~85 km long NCF multi-segment rupture. We therefore surmise that late Quaternary NCF surface rupturing earthquakes did not rupture through ~30-50° bends that link these segments. Our trench data and fault mapping also indicate lower slip rates on the Nevis segment than previous studies (0.04-0.1 mm/yr vs 0.4 mm/yr).</p> 2024-10-31T00:00:00-04:00 Copyright (c) 2024 Jack Williams, Mark Stirling, Robert Langridge, Govinda Niroula, Ashleigh Vause, James Stewart, Andy Nicol, Ninghseng Wang https://seismica.library.mcgill.ca/article/view/1345 Inelastic deformation accrued over multiple seismic cycles: Insights from an elastic-plastic slider-and-springboard model 2024-10-16T08:38:30-04:00 Pierre Dublanchet pierre.dublanchet@minesparis.psl.eu Jean-Arthur Olive jean.arthur.olive@gmail.com <p>We study a toy model designed to build physical insight into the problem of slow accumulation of non-recoverable strain in fault blocks over multiple earthquake cycles. The model consists of a thin, horizontal elastic-plastic plate (springboard) in frictional contact with a vertical, rigid wall moving downward at a steady speed. Our model produces stick-slip cycles consisting of interseismic plate downwarping and coseismic plate upwarping as long as the moment of the frictional force at the contact does not exceed the maximum (purely plastic) bending moment the plate can sustain. We show that the duration of individual earthquake cycles and the spatial pattern of interseismic deflection are controlled by two stress ratios involving the peak yield stress of the plate, the frictional strength of the fault and the coseismic stress drop. We show that non-recoverable plate deflection accumulates over successive earthquake cycles if the plate’s yield strength decreases through time, causing a progressive decrease of the aforementioned stress ratios. We derive scaling relations between the rate of accumulation of inelastic deformation, the relative tectonic plate velocity, and the rate of lithospheric weakening. Our results are consistent with observations of long-term permanent deformation of natural fault regions.</p> 2024-10-15T00:00:00-04:00 Copyright (c) 2024 Pierre Dublanchet, Jean-Arthur Olive https://seismica.library.mcgill.ca/article/view/1384 Putting faults in the northern Chilean subduction margin into motion: evidence for remote dynamic earthquake triggering on the plate interface and within the forearc 2024-11-06T12:43:35-05:00 Rebecca Harrington rebecca.harrington@rub.de Debi Kilb dkilb@ucsd.edu Marco Roth marco.roth@rub.de Pia Victor pvictor@gfz-potsdam.de Alessandro Verdecchia alessandro.verdecchia@rub.de <p>Dynamic stresses on the order of ~1 kPa from passing waves of mainshock earthquakes can trigger aftershocks at remote distances. Here, we investigate the prevalence of remote earthquake triggering in northern Chile, where aseismic-slip triggering has been documented. Our twofold approach to quantify triggerability includes a statistical difference-of-means test to quantify seismicity-rate changes bracketing candidate mainshock times, and a waveform-based approach to look for triggered earthquakes missing from the local catalog. We find no persistent, statistically-significant seismicity-rate increases associated with any of the candidate mainshocks when considering the local catalog in aggregate. However, catalog statistics reveal evidence for localized triggering both on the subduction interface and within the shallower forearc faults. Waveforms reveal local, uncataloged earthquakes only visible using a high-pass filter that removes the mainshock signal that otherwise overprints the local signals. Based on Japan mainshocks, we cannot rule out antipodal triggering. Areas showing higher triggerability are consistent with regions of low locking inferred from GNSS models and regions of observed aseismic slip. The spatial coincidence of triggering and low-locking, combined with the absence of a stress-triggering threshold, requires non-linear triggering mechanisms, such as altered frictional strength or aseismic-slip triggering, to be consistent with the observations.</p> 2024-11-06T00:00:00-05:00 Copyright (c) 2024 Rebecca Harrington, Debi Kilb, Marco Roth, Pia Victor, Alessandro Verdecchia https://seismica.library.mcgill.ca/article/view/1125 Seismic characteristics of the 2022-2023 unrest episode at Taupō volcano, Aotearoa New Zealand 2024-07-15T10:22:40-04:00 Oliver Lamb o.lamb@gns.cri.nz Stephen Bannister s.bannister@gns.cri.nz John Ristau j.ristau@gns.cri.nz Craig Miller c.miller@gns.cri.nz Steve Sherburn s.sherburn@gns.cri.nz Katie Jacobs k.jacobs@gns.cri.nz Jonathan Hanson j.hanson@gns.cri.nz Elisabetta D'Anastasio e.danastasio@gns.cri.nz Sigrún Hreinsdóttir s.hreinsdottir@gns.cri.nz Eveanjelene Snee eveanjelene@gmail.com Mike Ross m.ross@gns.cri.nz Eleanor Mestel el.mestel@vuw.ac.nz Finnigan Illsley-Kemp finnigan.illsleykemp@vuw.ac.nz <p>Taupō is a large caldera volcano located beneath a lake in the centre of the North Island of New Zealand and most recently erupted ~1800 years ago. The volcano has experienced at least 16 periods of unrest since 1872, each of which were characterised by increased seismic activity. Here we detail seismic activity during the most recent period of unrest from May 2022 to May 2023. The unrest was notable for the highest number of earthquakes detected during instrumented unrest episodes, and for one of the largest magnitude earthquakes detected beneath the lake for at least 50 years (M<sub>L</sub> 5.7). Relocated earthquakes indicate seismic activity was focused around an area hosting overlapping caldera structures and a hydrothermal system. Moment tensor inversion for the largest earthquake includes a non-negligible inflationary isotropic component. We suggest the seismic unrest was caused by the reactivation of faults due to an intrusion of magma at depth.</p> 2024-07-15T00:00:00-04:00 Copyright (c) 2024 Oliver Lamb, Stephen Bannister, John Ristau, Craig Miller, Steve Sherburn, Katie Jacobs, Jonathan Hanson, Elisabetta D'Anastasio, Sigrún Hreinsdóttir, Eveanjelene Snee, Mike Ross, Eleanor Mestel, Finnigan Illsley-Kemp https://seismica.library.mcgill.ca/article/view/1155 Strong asymmetry in near-fault ground velocity during an oblique strike-slip earthquake revealed by waveform particle motions and dynamic rupture simulations 2024-08-16T22:22:00-04:00 Jesse Kearse jesse@kearse.co.nz Yoshihiro Kaneko kaneko.yoshihiro.4e@kyoto-u.ac.jp Yoshito Nozuka nozuka.yoshito.75s@st.kyoto-u.ac.jp Christopher Milliner milliner@caltech.edu Ya-Ju Hsu yaru@earth.sinica.edu.tw Jean-Philippe Avouac avouac@caltech.edu <p>The 2022 Mw 7.0 Chihshang (Taiwan) earthquake, captured by almost a dozen near-fault strong-motion seismometers, high-rate GPS and satellite data, offers a rare opportunity to examine dynamic fault rupture in detail. Using dynamic rupture simulations, we investigate the particle motions recorded at near-fault strong-motion and 1 Hz GPS stations surrounding the main asperity. Some of these stations were as close as 250 m from the fault trace as determined by sub-pixel correlation of Sentinel-2 images. Our model reproduces the observed strong asymmetry in the ground motions on either side of the fault rupture, which results from along-dip spatial variability in rake angle on the steeply dipping fault (70°) at shallow depth (2 km). Observed near-fault, pulse-like fault-parallel ground velocity larger than fault-normal velocity can be explained by a model with a sub-shear rupture speed, which may be due to shallow rupture propagation within low-velocity material and to free surface reflections. In addition, we estimate a slip-weakening distance D<sub>c</sub> of ~0.7-0.9m from strong-motion seismogram recorded at Station F073, which is located ~250 m from the fault rupture, and the results of dynamic rupture modeling. The inferred D<sub>c</sub> is similar to other empirically derived estimates found for crustal earthquakes. These results have important implications for near-fault ground-motion hazard.</p> 2024-08-16T00:00:00-04:00 Copyright (c) 2024 Jesse Kearse, Yoshihiro Kaneko , Yoshito Nozuka , Christopher W.D. Milliner, Ya-Ju Hsu, Jean-Philippe Avouac https://seismica.library.mcgill.ca/article/view/1203 The influence of ground shaking on the distribution and size of coseismic landslides from the Mw 7.6 2005 Kashmir earthquake 2024-07-29T15:59:41-04:00 Audrey Dunham adunham@usgs.gov Eric Kiser ekiser@arizona.edu Jeffrey Kargel jkargel@psi.edu Umesh Haritashya uharitashya1@udayton.edu C. Scott Watson C.S.Watson@leeds.ac.uk Daniel Shugar daniel.shugar@ucalgary.ca <p>Understanding the conditions that governed the distribution of coseismic landslide frequency and size from past earthquakes is imperative for quantifying the hazard potential of future events. However, it remains a challenge to evaluate the many factors controlling coseismic landsliding including ground shaking, topography, rock strength, and hydrology, among others, for any given earthquake, partly due to the lack of direct seismic observations in high mountain regions. To address the dearth of ground motion observations near triggered landslides, we develop simulated ground motions, including topographic amplification, to investigate these key factors that control the distribution of coseismic landslides from the M<sub>w</sub> 7.6 2005 Kashmir earthquake. We show that the combination of strong peak ground motions, steep slopes, proximity to faults and rivers, and lithology control the overall spatial distribution of landslides. We also investigate the role of topographic amplification in triggering the largest landslide induced by this earthquake, the Hattian Bala landslide, finding that it is amplified at the landslide initiation point due to the trapping of energy within the ridge kink as it changes orientation from E to NE. This focusing effect combined with predisposing conditions for hillslope failure may have influenced the location and size of this devastating landslide.</p> 2024-07-29T00:00:00-04:00 Copyright (c) 2024 Audrey Dunham, Eric Kiser, Jeffrey Kargel, Umesh Haritashya, C. Scott Watson, Daniel Shugar https://seismica.library.mcgill.ca/article/view/1341 DeepRFQC: automating quality control for P-wave receiver function analysis using a U-net inspired network 2024-07-30T14:02:43-04:00 Sina Sabermahani sabermas@myumanitoba.ca Andrew Frederiksen andrew.frederiksen@umanitoba.ca <p>This paper introduces DeepRFQC, an automated method for quality control in P-wave receiver function analysis. Leveraging a U-Net inspired deep learning model, which has previously shown promise in denoising and phase detection, DeepRFQC efficiently distinguishes usable from noisy receiver functions. We examine a Proterozoic Trans-Hudson Orogen dataset from northern Canada, including seismic events from 1990 to 2023, which is expanded for training purposes by data augmentation techniques. With 1,508,449 trainable parameters, the DeepRFQC model attains a commendable 96.6% validation accuracy, on a test dataset from the X5 seismic network; tests on stations from different tectonic environments indicate that the model is effective even in environments very different from the training set. Validation through the H-κ stacking method shows consistent and plausible results. As manual quality control is a major bottleneck in receiver-function processing, automated methods such as this one will allow for efficient examination of large data sets.</p> 2024-11-12T00:00:00-05:00 Copyright (c) 2024 Sina Sabermahani, Andrew Frederiksen https://seismica.library.mcgill.ca/article/view/1374 Population displacement after earthquakes: benchmarking predictions based on housing damage 2024-10-28T17:31:30-04:00 Nicole Paul nicole.paul.22@ucl.ac.uk Carmine Galasso c.galasso@ucl.ac.uk Vitor Silva vitor.silva@globalquakemodel.org Jack Baker bakerjw@stanford.edu <p>In the aftermath of an earthquake, the number of residents whose housing was destroyed is often used to approximate the number of people displaced (i.e., rendered homeless) after the event. While this metric can provide rapid situational awareness regarding potential long-term housing needs, more recent research highlights the importance of additional factors beyond housing damage within the scope of household displacement and return (e.g., utility disruption, tenure, place attachment). This study benchmarks population displacement estimates using this simplified conventional approach (i.e., only considering housing destruction) through three scenario models for recent earthquakes in Haiti, Japan, and Nepal. These model predictions are compared with officially reported values and alternate mobile location data-based estimates from the literature. The results highlight the promise of scenario models to realistically estimate population displacement and potential long-term housing needs after earthquakes, but also highlight a large range of uncertainty in the predicted values. Furthermore, purely basing displacement estimates on housing damage offers no view on how the displaced population counts vary with time as compared to more comprehensive models that include other factors influencing population return or alternative approaches, such as using mobile location data.</p> 2024-10-28T00:00:00-04:00 Copyright (c) 2024 Nicole Paul, Carmine Galasso, Vitor Silva, Jack Baker https://seismica.library.mcgill.ca/article/view/1184 DASCore: a Python Library for Distributed Fiber Optic Sensing 2024-07-30T09:55:22-04:00 Derrick Chambers derchambers@cdc.gov Ge Jin gjin@mines.edu Ahmad Tourei tourei@mines.edu Abdul Hafiz Saeed Issah aissah@mines.edu Ariel Lellouch ariellel@tauex.tau.ac.il Eileen Martin eileenrmartin@mines.edu Donglin Zhu dzhu@mines.edu Aaron Girard agirard@mines.edu Shihao Yuan syuan@mines.edu Thomas Cullison tculliso@sep.stanford.edu Tomas Snyder tsnyder1@mines.edu Seunghoo Kim seunghoo@stanford.edu Nicholas Danes ndanes@mines.edu Nikhil Punithan nikhil_punithan@mines.edu M. Shawn Boltz ynt2@cdc.gov Manuel M. Mendoza manuel.mendoza@colorado.edu <p>In the past decade, distributed acoustic sensing (DAS) has enabled many new monitoring applications in diverse fields including hydrocarbon exploration and extraction; induced, local, regional, and global seismology; infrastructure and urban monitoring; and several others. However, to date, the open-source software ecosystem for handling DAS data is relatively immature. Here we introduce DASCore, a Python library for analyzing, visualizing, and managing DAS data. DASCore implements an object-oriented interface for performing common data processing and transformations, reading and writing various DAS file types, creating simple visualizations, and managing file system-based DAS archives. DASCore also integrates with other Python-based tools which enable the processing of massive data sets in cloud environments. DASCore is the foundational package for the broader DAS data analysis ecosystem (DASDAE), and as such its main goal is to facilitate the development of other DAS libraries and applications.</p> 2024-07-30T00:00:00-04:00 Copyright (c) 2024 Derrick Chambers, Ge Jin, Ahmad Tourei, Abdul Hafiz Saeed Issah, Ariel Lellouch, Eileen Martin, Donglin Zhu, Aaron Girard, Shihao Yuan, Thomas Cullison, Tomas Snyder, Seunghoo Kim, Nicholas Danes, Nikhil Punithan, M. Shawn Boltz, Manuel M. Mendoza https://seismica.library.mcgill.ca/article/view/1339 Development and Comparison of 3D Seismic Geology and Shear-wave Velocity Models of Metro Vancouver 2024-04-17T11:43:27-04:00 Sujan Adhikari Sadhika6@uwo.ca Sheri Molnar smolnar8@uwo.ca <p>This study presents a 3D regional modeling of seismic geology and shear wave velocity (Vs) in Metro Vancouver for seismic microzonation and hazard prediction. Leveraging an extensive geodatabase compiled from invasive and non-invasive in situ data, including lithological logs and seismic field data, we delineated four major geological units: Holocene post-glacial and Pleistocene inter/glacial sediments, and Tertiary sedimentary and Pre-Tertiary Coast Mountain plutonic rocks.</p> <p>Seismic geology model integrates the four primary geological formations, leveraging significant impedance-based surfaces derived from meticulously analyzed borehole stratigraphic logs and Vs depth profiles sourced from 2333 georecords, enhancing its depth and accuracy. Through a meticulous comparison with established interpreted geological cross-sections, we have reaffirmed the robustness and reliability of our seismic geology modeling approach. A numerical 3D “geotechnical layer” Vs model with 11 isovelocity surfaces was developed using 688 Vs depth profiles. Comparison with microtremor amplification spectra confirms our 3D models' reliable use in predicting site amplification. We find that the combination of local geology (thicknesses) and Vs information outperforms prediction in fundamental peak frequency compared to using only local geology combined with regional Vs information. Our study contributes to advancing understanding of seismic hazards in Metro Vancouver, highlighting the importance of incorporating localized seismic site conditions for precise regional seismic hazard assessments.</p> 2024-09-12T00:00:00-04:00 Copyright (c) 2024 Sujan Adhikari, Sheri Molnar https://seismica.library.mcgill.ca/article/view/1179 Investigation of suspected Holocene fault scarp near Montréal, Québec: The first paleoseismic trench in eastern Canada 2024-07-25T09:16:05-04:00 Aube Gourdeau aube.gourdeau@mail.mcgill.ca Veronica B. Prush veronica.prush@nmt.edu Christie D. Rowe christie.rowe@mcgill.ca Claudine Nackers claudine.nackers@polymtl.ca Hannah Mark hmark@whoi.edu Isabel Morris isabel.svoboda@nmt.edu Philippe Rosset philippe.rosset@affiliate.mcgill.ca Michel Lamothe lamothe.michel@uqam.ca Luc Chouinard luc.chouinard@mcgill.ca Matthew S. Tarling tarlingmatthew@gmail.com <p>Québec has experienced historical damaging earthquakes in several seismic zones (e.g. 1732 M5.8 Montréal, 1663 M7 Charlevoix, 1935 M6.2 Témiscamingue). Despite a high seismicity rate, no surface-rupturing faults have been discovered due to a combination of dense vegetation cover, recent glaciation, sparse earthquake records, and low regional strain rates. We manually searched lidar-derived digital elevation models (DEMs) of the region to search for potential post-glacial surface-rupturing faults across southern Québec and identified a scarp ~50km north of Montréal. We performed three geophysical surveys (ground penetrating radar, depth estimates from ambient seismic noise, and refraction seismology) that revealed a buried scarp, confirmed with a &lt;1 m-deep hand-dug test pit. These observations convinced us to excavate the first paleoseismic trench in Québec to test for the presence of a surface-rupturing fault in July 2023. We found a glacial diamict containing no signs of syn- or post-glacial deformation. In this paper, we present the observations that led to the identification of a scarp and hypothesized faulting. We highlight the importance of trenching to confirm recent fault scarps in challenging environments. We hope our study can be used to optimize future paleoseismic research in the province of Québec and similar intracratonic glaciated landscapes.</p> 2024-07-25T00:00:00-04:00 Copyright (c) 2024 Aube Gourdeau, Veronica B. Prush, Christie D. Rowe, Claudine Nackers, Hannah Mark, Isabel Morris, Philippe Rosset, Michel Lamothe, Luc Chouinard, Matthew S. Tarling https://seismica.library.mcgill.ca/article/view/1394 Source characterization of the 20th May 2024 MD 4.4 Campi Flegrei caldera earthquake through a joint source-propagation probabilistic inversion 2024-08-05T19:09:17-04:00 Mariano Supino mariano.supino@ingv.it Laura Scognamiglio laura.scognamiglio@ingv.it Lauro Chiaraluce lauro.chiaraluce@ingv.it Carlo Doglioni carlo.doglioni@ingv.it Andrè Herrero andre.herrero@ingv.it <p>On May 20<sup>th</sup>, 2024, an earthquake of magnitude <em>M<sub>D</sub></em> 4.4 nucleated at shallow depth (2.6 km) in the Campi Flegrei caldera (Southern Italy), a densely populated area where an increase in seismic activity has been observed since 2019 attributable to an on-going unrest episode. While the magnitude was moderate, the event produced a strong ground shaking with an observed maximum peak ground acceleration of 3.58 m s<sup>-2</sup>, and several buildings were damaged. Here, we characterize the earthquake source using a probabilistic joint source-propagation spectral inversion in the Fourier space. We estimate a moment magnitude <em>M<sub>w</sub></em> = 3.70 ± 0.13 and a corner frequency <em>f<sub>c</sub></em> = 1.11 ± 0.19 Hz. Assuming a circular rupture model, we estimate a source radius <em>r</em> = 400 ± 70 m and a stress drop <em>Δσ</em> = 3.2 ± 2.2 MPa. The estimated stress drop suggests that future earthquakes in the hypocentral region, considering a possible rupture length of 3 km suggested by previous studies, can have magnitude increased by 1.2 ± 0.3 units with respect to May 20<sup>th </sup>event. A systematic source characterization of the recent seismicity in the caldera would hep in estimating the expected ground motions from future large-magnitude events. </p> 2024-08-05T00:00:00-04:00 Copyright (c) 2024 Mariano Supino, Laura Scognamiglio, Lauro Chiaraluce, Carlo Doglioni, Andrè Herrero https://seismica.library.mcgill.ca/article/view/1405 Earthquake source inversion by integrated fiber-optic sensing 2024-07-22T09:40:26-04:00 Nils Müller nilmueller@student.ethz.ch Sebastian Noe sebastian.noe@erdw.ethz.ch Dominik Husmann Dominik.Husmann@metas.ch Jacques Morel Jacques.Morel@metas.ch Andreas Fichtner andreas.fichtner@erdw.ethz.ch <p style="font-weight: 400;">We present an earthquake source inversion using a single time series produced by integrated fiber-optic sensing in a phase noise cancellation (PNC) system used for frequency metrology. Operating on a 123 km long fiber between Bern and Basel (Switzerland), the PNC system recorded the Mw3.9 Mulhouse earthquake that occurred on 10 September 2022 around 10 km north-west of the northern fiber end.&nbsp; A generalised least-squares inversion in the 4 - 13 s period band constrains the components of a double-couple moment tensor with an uncertainty that corresponds to around 0.2 moment magnitude units, nearly independent of prior information.&nbsp; Uncertainties for hypocenter location and original time are more variable, ranging between 4 - 20 km and 0.1 - 1 s, respectively, depending on whether injected prior information is realistic or almost absent.&nbsp; This work is a proof of concept that quantifies the resolvability of earthquake source properties under specific conditions using a single-channel stand-alone integrated (non-distributed) fiber-optic measurement.&nbsp; It thereby constitutes a step towards the integration of long-range phase-transmission fiber-optic sensors into existing seismic networks in order to fill significant seismic data gaps, especially in the oceans.</p> 2024-07-22T00:00:00-04:00 Copyright (c) 2024 Nils Müller, Sebastian Noe, Dominik Husmann, Jacques Morel, Andreas Fichtner