Bulletin of the Seismological Society of America最新文献

{"title":"Kinematic Rupture Model of the 6 February 2023 Mw 7.8 Türkiye Earthquake from a Large Set of Near-Source Strong-Motion Records Combined with GNSS Offsets Reveals Intermittent Supershear Rupture","authors":"Bertrand Delouis, Martijn van den Ende, Jean-Paul Ampuero","doi":"10.1785/0120230077","DOIUrl":"https://doi.org/10.1785/0120230077","url":null,"abstract":"ABSTRACT The 2023 Mw 7.8 southeast Türkiye earthquake was recorded by an unprecedentedly large set of strong-motion stations very close to its rupture, opening the opportunity to observe the rupture process of a large earthquake with fine resolution. Here, the kinematics of the earthquake source are inferred by finite-source inversion based on strong-motion records and coseismic offsets from permanent Global Navigation Satellite Systems stations. The strong-motion records at stations NAR and 4615, which are the closest to the splay fault (SPF) where the rupture initiated and which were previously interpreted to contain the signature of supershear rupture speeds, are successfully modeled here by a subshear rupture propagating unilaterally to the northeast. Once the rupture on the SPF reaches the east Anatolian fault (EAF), it propagates on the EAF bilaterally, extending about 120 km northeast and 180 km southwest. To the south, the depth extent of the rupture decreases, as it passes a bend of the EAF. Although the rupture velocity remains globally subshear along the EAF, we identify three portions of the fault where the rupture is transiently supershear. The transitions to supershear speed coincide with regions of reduced fault slip, which suggests supershear bursts generated by the failure of local rupture barriers. Toward the southwest termination, the rupture encircles an asperity before its failure, which is a feature that has been observed only on rare occasions. This unprecedented detail of the inversion was facilitated by the proximity to the fault and the exceptional density of the accelerometric network in the area.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":" 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135241831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reply to “Comment on ‘Effect of Style of Faulting on the Orientation of Maximum Horizontal Earthquake Response Spectra’ by Alan Poulos and Eduardo Miranda” by Paul Somerville","authors":"Alan Poulos, Eduardo Miranda","doi":"10.1785/0120230223","DOIUrl":"https://doi.org/10.1785/0120230223","url":null,"abstract":"Reply| November 09, 2023 Reply to “Comment on ‘Effect of Style of Faulting on the Orientation of Maximum Horizontal Earthquake Response Spectra’ by Alan Poulos and Eduardo Miranda” by Paul Somerville Alan Poulos; Alan Poulos * 1Department of Civil and Environmental Engineering, Stanford University, Stanford, California, U.S.A. *Corresponding author: apoulos@stanford.edu https://orcid.org/0000-0001-8654-1024 Search for other works by this author on: GSW Google Scholar Eduardo Miranda Eduardo Miranda 1Department of Civil and Environmental Engineering, Stanford University, Stanford, California, U.S.A. https://orcid.org/0000-0001-9398-443X Search for other works by this author on: GSW Google Scholar Author and Article Information Alan Poulos https://orcid.org/0000-0001-8654-1024 * 1Department of Civil and Environmental Engineering, Stanford University, Stanford, California, U.S.A. Eduardo Miranda https://orcid.org/0000-0001-9398-443X 1Department of Civil and Environmental Engineering, Stanford University, Stanford, California, U.S.A. *Corresponding author: apoulos@stanford.edu Publisher: Seismological Society of America First Online: 09 Nov 2023 Online ISSN: 1943-3573 Print ISSN: 0037-1106 © Seismological Society of America Bulletin of the Seismological Society of America (2023) https://doi.org/10.1785/0120230223 Article history First Online: 09 Nov 2023 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Alan Poulos, Eduardo Miranda; Reply to “Comment on ‘Effect of Style of Faulting on the Orientation of Maximum Horizontal Earthquake Response Spectra’ by Alan Poulos and Eduardo Miranda” by Paul Somerville. Bulletin of the Seismological Society of America 2023; doi: https://doi.org/10.1785/0120230223 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search We thank Somerville (2023) for the comment on our article (Poulos and Miranda, 2023), which found that the orientation of maximum horizontal spectral response tends to be close to the transverse orientation with respect to the epicenter of strike‐slip earthquakes. Herein, we respond to the main points of the comment, following the order in which they were made. In the comment, Somerville (2023) mentions that “Using a point‐source model of the earthquake source, they find that…”. It should be noted that in our study, we do not explicitly use a point‐source model other than when computing the transverse... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":" 10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135241842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhancement of Seismic Phase Identification Using Polarization Filtering and Array Analysis","authors":"On Ki Angel Ling, Simon C. Stähler, David Sollberger, Domenico Giardini","doi":"10.1785/0120230135","DOIUrl":"https://doi.org/10.1785/0120230135","url":null,"abstract":"ABSTRACT Seismic arrays play a crucial role in identifying weak signals in the seismic wavefield based on their expected slowness and backazimuth values. However, their resolution power is limited when studying phases with similar horizontal slownesses and arrival times, such as receiver-side or source-side reverberations and converted phases. Therefore, we investigate the benefit of applying polarization filtering to three-component seismograms before stacking to remove undesired signals and increase the signal-to-noise ratio of the array. Customized polarization filters enable more sophisticated wavefield separation and robust phase identification on vespagrams. However, selecting the suitable polarization filter requires a balance between noise reduction and the preservation of desired signals. We find that degree-of-polarization filters generally excel in suppressing incoherent noise. On the other hand, some filters, for example, based solely on ellipticity, do not yield notable enhancements for body waves and may even produce adverse effects, specifically for phases that arrive late in the seismogram. We demonstrate these findings using data recorded by AlpArray and surrounding permanent stations.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"291 9","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135474706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evidence of Seattle Fault Earthquakes from Patterns in Deep-Seated Landslides","authors":"Erich Herzig, Alison Duvall, Adam Booth, Ian Stone, Erin Wirth, Sean LaHusen, Joseph Wartman, Alex Grant","doi":"10.1785/0120230079","DOIUrl":"https://doi.org/10.1785/0120230079","url":null,"abstract":"ABSTRACT Earthquake-induced landslides can record information about the seismic shaking that generated them. In this study, we present new mapping, Light Detection and Ranging-derived roughness dating, and analysis of over 1000 deep-seated landslides from the Puget Lowlands of Washington, U.S.A., to probe the landscape for past Seattle fault earthquake information. With this new landslide inventory, we observe spatial and temporal evidence of landsliding related to the last major earthquake on the Seattle fault ∼1100 yr before present. We find spatial clusters of landslides that correlate with ground motions from recent 3D kinematic models of Seattle fault earthquakes. We also find temporal patterns in the landslide inventory that suggest earthquake-driven increases in landsliding. We compare the spatial and temporal landslide data with scenario-based ground motion models and find stronger evidence of the last major Seattle fault earthquake from this combined analysis than from spatial or temporal patterns alone. We also compare the landslide inventory with ground motions from different Seattle fault earthquake scenarios to determine the ground motion distributions that are most consistent with the landslide record. We find that earthquake scenarios that best match the clustering of ∼1100-year-old landslides produce the strongest shaking within a band that stretches from west to east across central Seattle as well as along the bluffs bordering the broader Puget Sound. Finally, we identify other landslide clusters (at 4.6–4.2 ka, 4.0–3.8 ka, 2.8–2.6 ka, and 2.2–2.0 ka) in the inventory which let us infer potential ground motions that may correspond to older Seattle fault earthquakes. Our method, which combines hindcasting of the surface response to the last major Seattle fault earthquake, using a roughness-aged landslide inventory with forecasts of modeled ground shaking from 3D seismic scenarios, showcases a powerful new approach to gleaning paleoseismic information from landscapes.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"291 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135474712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Upper Plate and Subduction Interface Deformation Models in the 2022 Revision of the Aotearoa New Zealand National Seismic Hazard Model","authors":"Russ J. Van Dissen, Kaj M. Johnson, Hannu Seebeck, Laura M. Wallace, Chris Rollins, Jeremy Maurer, Matthew C. Gerstenberger, Charles A. Williams, Ian J. Hamling, Andrew Howell, Christopher J. DiCaprio","doi":"10.1785/0120230118","DOIUrl":"https://doi.org/10.1785/0120230118","url":null,"abstract":"ABSTRACT As part of the 2022 revision of the Aotearoa New Zealand National Seismic Hazard Model (NZ NSHM 2022), deformation models were constructed for the upper plate faults and subduction interfaces that impact ground-shaking hazard in New Zealand. These models provide the locations, geometries, and slip rates of the earthquake-producing faults in the NZ NSHM 2022. For upper plate faults, two deformation models were developed: a geologic model derived directly from the fault geometries and geologic slip rates in the NZ Community Fault Model version 1.0 (NZ CFM v.1.0); and a geodetic model that uses the same faults and fault geometries and derives fault slip-deficit rates by inverting geodetic strain rates for back slip on those specified faults. The two upper plate deformation models have similar total moment rates, but the geodetic model has higher slip rates on low-slip-rate faults, and the geologic model has higher slip rates on higher-slip-rate faults. Two deformation models are developed for the Hikurangi–Kermadec subduction interface. The Hikurangi–Kermadec geometry is a linear blend of the previously published interface models. Slip-deficit rates on the Hikurangi portion of the deformation model are updated from the previously published block models, and two end member models are developed to represent the alternate hypotheses that the interface is either frictionally locked or creeping at the trench. The locking state in the Kermadec portion is less well constrained, and a single slip-deficit rate model is developed based on plate convergence rate and coupling considerations. This single Kermadec realization is blended with each of the two Hikurangi slip-deficit rate models to yield two overall Hikurangi–Kermadec deformation models. The Puysegur subduction interface deformation model is based on geometry taken directly from the NZ CFM v.1.0, and a slip-deficit rate derived from published geodetic plate convergence rate and interface coupling estimates.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"42 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135820027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deep Learning-Based Microseismic Detection and Location Reveal the Seismic Characteristics and Causes in the Xiluodu Reservoir, China","authors":"Ziyi Li, Lianqing Zhou, Mengqiao Duan, Cuiping Zhao","doi":"10.1785/0120230134","DOIUrl":"https://doi.org/10.1785/0120230134","url":null,"abstract":"ABSTRACT The Xiluodu reservoir, as the third reservoir developed in the lower Jinsha River, is the fourth largest reservoir in the world in terms of power generation. It is located in an area of historically high seismic intensity. A large amount of seismic activity has occurred in the reservoir area because the reservoir was impounded in 2013, but the mechanism of seismogenesis is still not clear. In this study, we collected continuous seismic records from July 2020 to October 2022 in the Xiluodu reservoir area, built a high-precision microseismic catalog for this region based on a deep learning seismic detection and location workflow called LOC-FLOW, and eventually obtained high-precision locations of 4924 earthquakes (five times more than the routine catalog). We sketched the main seismogenic structures based on the spatial and temporal distribution of the earthquakes in the catalog. According to the relationship between periodic variation of water level and seismic activity, seismicity in the reservoir area is active at the stage when the water level is filling to the highest point and starts to draw down. Especially, the sudden change in the rate of water level variation can easily trigger seismic activity. Combined with the spatiotemporal distribution of seismicity in each region and the previous results of numerical simulation, we concluded that the seismic activity in the reservoir head area and around the Manao fault is likely induced by the increase of normal stress and pore pressure diffusion caused by reservoir impoundment, whereas the ML 4.6 earthquake that occurred at the intersection of the Lianfeng fault and the Zhongcun fault was likely tectonic activity occurring on a concealed fault.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"125 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135326082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Construction of a Ground-Motion Logic Tree through Host-to-Target Region Adjustments Applied to an Adaptable Ground-Motion Prediction Model: An Addendum","authors":"David M. Boore","doi":"10.1785/0120230143","DOIUrl":"https://doi.org/10.1785/0120230143","url":null,"abstract":"ABSTRACT Boore et al. (2022; hereafter, Bea22) described adjustments to a host-region ground-motion prediction model (GMPM) for use in hazard calculations in a target region, using Chiou and Youngs (2014; hereafter, CY14) as the host-region model. This article contains two modifications to the Bea22 procedures for the host-to-target adjustments, one for the source and one for the anelastic attenuation function. The first modification is to compute logic-tree branches for the source adjustment variable ΔcM given in Bea22 assuming that the host- and target-region stress parameters are uncorrelated, instead of the implicit assumption in Bea22 that they are perfectly correlated. The assumption of uncorrelated stress parameters makes little difference for the example in Bea22 because the standard deviation of the host-region stress parameter is much less than that of the target-region stress parameter. However, this might not be the case in some future applications. The second modification is to the host-to-target anelastic attenuation path adjustment. The adjustment in Bea22 involves a distance-independent change in the γ variable that controls the rate of anelastic attenuation in the CY14 GMPM. This article proposes a method to account for a distance dependence in the adjustment. Such a dependence is needed for short-period ground-motion intensity measures (GMIMs) at distances greater than 100 km, with the importance increasing with distance. For the example in Bea22, the ratio of GMIMs computed with the revised and the previous adjustment to γ is less than about a factor of 1.05 at distances within about 100 km, but it can exceed a factor of 2 at 300 km for short-period GMIMs.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"26 29","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135863318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Population-Based Performance Evaluation of the ShakeAlert Earthquake Early Warning System for <i>M</i> 9 Megathrust Earthquakes in the Pacific Northwest, U.S.A.","authors":"Mika Thompson, J. Renate Hartog, Erin A. Wirth","doi":"10.1785/0120230055","DOIUrl":"https://doi.org/10.1785/0120230055","url":null,"abstract":"ABSTRACT We evaluate the potential performance of the ShakeAlert earthquake early warning system for M 9 megathrust earthquakes in the Pacific Northwest (PNW) using synthetic seismograms from 30 simulated M 9 earthquake scenarios on the Cascadia subduction zone. The timeliness and accuracy of source estimates and effectiveness of ShakeAlert alert contours are evaluated with a station-based alert classification scheme using an alert threshold equal to the target threshold. We develop a population-based alert classification method by aligning a population grid with Voronoi diagrams computed from the station locations for each scenario. Using raster statistics, we estimate the PNW population that would receive timely accurate alerts during an offshore M 9 earthquake. We also examine the range of expected warning times with respect to the spatial distribution of the population. Results show that most of the population in our evaluation region could receive alerts with positive warning times for an alert threshold of modified Mercalli intensity (MMI) III, but that late and missed alerts increase because the alert threshold is increased. An average of just under 60% of the population would be alerted for MMI V prior to the arrival of threshold level shaking. Large regions of late and missed alerts for thresholds MMI IV and V are caused by delays in alert updates, inaccurate FinDer source estimates, and undersized alert contours due to magnitude underestimation. We also investigate an alerting strategy where ShakeAlert sends out an alert to the entire evaluation region when the system detects at least an M 8 earthquake along the coast. Because large magnitude offshore earthquakes are rare in Cascadia, overalerting is most likely to occur from an overestimated M 7+ on the Gorda plate. With appropriate criteria to minimize overalerting, this strategy may eliminate all missed and late alerts except at sites close to the epicenter.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"2016 34","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135813996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New Zealand Fault-Rupture Depth Model v.1.0: A Provisional Estimate of the Maximum Depth of Seismic Rupture on New Zealand’s Active Faults","authors":"Susan Ellis, Stephen Bannister, Russ Van Dissen, Donna Eberhart-Phillips, Carolyn Boulton, Martin Reyners, Rob Funnell, Nick Mortimer, Phaedra Upton, Chris Rollins, Hannu Seebeck","doi":"10.1785/0120230166","DOIUrl":"https://doi.org/10.1785/0120230166","url":null,"abstract":"ABSTRACT We summarize estimates of the maximum rupture depth on New Zealand’s active faults (“New Zealand Fault-Rupture Depth Model v.1.0”), as used in the New Zealand Community Fault Model v1.0 and as a constraint for the latest revision of the New Zealand National Seismic Hazard Model (NZ NSHM 2022). Rupture depth estimates are based on a combination of two separate model approaches (using different methods and datasets). The first approach uses regional seismicity distribution from a relocated earthquake catalog to calculate the 90% seismicity cutoff depth (D90), representing the seismogenic depth limit. This is multiplied by an overshoot factor representing the dynamic propagation of rupture into the conditional stability zone, and accounting for the difference between regional seismicity depths and the frictional properties of a mature fault zone to arrive at a seismic estimate of the maximum rupture depth. The second approach uses surface heat flow and rock type to compute depths that correspond to the thermal limits of frictional instabilities on seismogenic faults. To arrive at a thermally-based maximum rupture depth, these thermal limits are also multiplied by an overshoot factor. Both the models have depth cutoffs at the Moho and/or subducting slabs. Results indicate the maximum rupture depths between 8 (Taupō volcanic zone) and &amp;gt;30 km (e.g., southwest North Island), strongly correlated with regional thermal gradients. The depths derived from the two methods show broad agreement for most of the North Island and some differences in the South Island. A combined model using weighting based on relative uncertainties is derived and validated using constraints from hypocenter and slip model depths from recent well-instrumented earthquakes. We discuss modifications to the maximum rupture depths estimated here that were undertaken for application within the NZ NSHM 2022. Our research demonstrates the utility of combining seismicity cutoff and thermal stability estimates to assess the down-dip dimensions of future earthquake ruptures.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"55 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136233556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Seismogenic Slab Source Model for Aotearoa New Zealand","authors":"Kiran Kumar Singh Thingbaijam, Matt C. Gerstenberger, Chris Rollins, Russ J. Van Dissen, Sepideh J. Rastin, Annemarie Christophersen, John Ristau, Charles A. Williams, Delphine D. Fitzenz, Marco Pagani","doi":"10.1785/0120230080","DOIUrl":"https://doi.org/10.1785/0120230080","url":null,"abstract":"Abstract Intraslab seismicity within the Hikurangi and Puysegur subduction zones constitutes &amp;gt;50% of recorded (Mw≥4.0 events) earthquakes in Aotearoa New Zealand. Here, we develop a source model for intraslab seismicity using recently augmented datasets including models of subduction interface geometries, an earthquake catalog, and a regional moment tensor catalog. For the areal zones of uniform seismicity, we consider the whole of each slab, as well as demarcations between shallower (depth ≤40 km) and deeper regions. Thereafter, we evaluate the magnitude–frequency distributions in each zone. To compute smoothed seismicity distributions, we apply a novel quasi-3D approach that involve: (1) delineation of midslab surfaces (defined by regions of maximum earthquake density), (2) orthogonal projections of hypocenters onto the midslab profiles, (3) uniform gridding of 0.1° down-dip on the midslab, and (4) application of smoothing kernel on the projected hypocenters. We also develop a model to characterize the focal mechanisms of the intraslab earthquakes using the regional moment tensor catalog. This model has median strike angles subparallel to subduction trenches and median dip angles ≥60° in both the subduction zones. The distribution of rake angles suggests that the Hikurangi slab has an extensional regime in the shallower parts but a compressional regime in the deeper parts, indicative of slab flexure. In contrast, the Puysegur slab predominantly exhibits a compressional regime.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"178 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136233427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}