Journal of Geophysical Research: Solid Earth最新文献

{"title":"AI-PAL: Self-Supervised AI Phase Picking via Rule-Based Algorithm for Generalized Earthquake Detection","authors":"Yijian Zhou,&nbsp;Hongyang Ding,&nbsp;Abhijit Ghosh,&nbsp;Zengxi Ge","doi":"10.1029/2025JB031294","DOIUrl":"https://doi.org/10.1029/2025JB031294","url":null,"abstract":"<p>Delineating fault structures through microseismicity is crucial for earthquake hazard assessment, yet constructing high-resolution catalogs over extended periods remains challenging. This study introduces AI-PAL, a novel deep learning-driven workflow that employs a Self-Attention RNN (SAR) model trained with detections from PAL, an established rule-based algorithm (Zhou, Yue, et al., 2021, https://doi.org/10.1785/0220210111), for generalized earthquake detection. PAL utilizes short-term-average over long-term-average algorithm for event detection, ensuring consistent performance across different datasets. AI-PAL leverages these rule-based picks as training labels, enabling self-supervised learning of the SAR model across arbitrary regions, thereby enhancing PAL's detection capabilities. We applied SAR-PAL to two distinct regions that are featured by recent large earthquakes: (a) the preseismic period of the Ridgecrest-Coso region (2008–2019), and (b) the pre-to-postseismic period of the East Anatolian Fault Zone (EAFZ, 2020–2023/04). Our results demonstrate that SAR-PAL offers slightly higher detection completeness than the quake template matching matched filter catalog, while boosts over 100 times faster processing and a superior temporal stability, avoiding detection gaps during background periods. Compared to PhaseNet and GaMMA, two widely recognized phase picker and associator, SAR-PAL proved more scalable, achieving ∼2.5 times more event detections in the EAFZ case, along with a ∼7 times higher phase association rate. We further experimented training PhaseNet and SAR with PAL detections and routine catalogs, and found that no other combinations matched the detection performance of SAR-PAL. The enhanced catalogs built by SAR-PAL reveals geometrical complexities of the Ridgecrest faults and the Erkenek-Pütürge segment of EAFZ, offering insights into their contrasting roles during the large earthquake.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JB031294","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143717245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comprehensive Evaluation of DAS Amplitude and Its Implications for Earthquake Early Warning and Seismic Interferometry","authors":"Qiushi Zhai,&nbsp;Jiuxun Yin,&nbsp;Yan Yang,&nbsp;James W. Atterholt,&nbsp;Jiaxuan Li,&nbsp;Allen Husker,&nbsp;Zhongwen Zhan","doi":"10.1029/2024JB030288","DOIUrl":"https://doi.org/10.1029/2024JB030288","url":null,"abstract":"<p>Distributed Acoustic Sensing (DAS) is an emerging technology that converts optical fibers into dense arrays of strainmeters, significantly enhancing our understanding of earthquake physics and Earth's structure. While most past DAS studies have focused primarily on seismic wave phase information, accurate measurements of true ground motion amplitudes are crucial for comprehensive future analyses. However, amplitudes in DAS recordings, especially for pre-existing telecommunication cables with uncertain fiber-ground coupling, have not been fully quantified. By calibrating three DAS arrays with co-located seismometers, we systematically evaluate DAS amplitudes. Our results indicate that the average DAS amplitude of earthquake signals closely matches that of co-located seismometer data across frequencies from 0.01 to 10 Hz. The noise floor of DAS is comparable to that of strong-motion stations but higher than that of broadband stations. The saturation amplitude of DAS is adjustable by modifying the pulse repetition rate and gauge length. We also demonstrate how our findings enhance the understanding of fiber-optic seismology and its implications for natural hazard mitigation and Earth structure imaging and monitoring. Specifically, our results suggest that with proper settings, DAS can detect <i>P</i>-waves from an M6+ earthquake occurring 10 km from the cable without saturation, indicating its viability for earthquake early warning. Through quantitative comparison and analysis, we also find that local ambient traffic noise levels strongly affect the quality of seismic interferometry measurement, which is a powerful tool for near-surface imaging and monitoring. Our methodology and findings are valuable for future DAS experiments that require precise seismic amplitude measurements.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143717246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Role of Grain Size on Shear Localization Illuminated by Acoustic Emissions","authors":"N. Casas,&nbsp;C. Giorgetti,&nbsp;F. Pignalberi,&nbsp;M. M. Scuderi","doi":"10.1029/2024JB030448","DOIUrl":"https://doi.org/10.1029/2024JB030448","url":null,"abstract":"<p>Shear localization within the fault core, as evidenced by grain comminution in fault gouge, plays a crucial role in the initiation of frictional instabilities. To upscale the physics of shear localization and understand the influence of grain size, it is essential to identify the governing physical parameters and micro-mechanisms. In this study, we conducted double-direct shear experiments on quartz fault gouges with varying initial grain sizes (coarse, small, and bi-disperse mixtures) under constant normal stress and shearing velocity, while continuously monitoring Acoustic Emissions (AE). Microstructural analyses were performed on the deformed samples to complement the mechanical and AE data. Our results reveal that, while the initial grain size and distribution do not substantially alter the steady-state friction coefficient, they significantly influence the early stages of frictional evolution leading to a steady state, which is reflected in a different rate and amplitude of AEs. Specifically, coarse grains and bi-disperse mixtures exhibit strain-hardening behavior before reaching steady-state friction, whereas fine grains show strain-weakening behavior. Microstructural observations further indicate that bi-disperse mixtures retard the localization of deformation with increasing fault displacement. The AE data shows a strong dependence on both the average grain size and the evolving state of the gouge layer. Notably, there is a direct correlation between b-value evolution and the average grain size within the gouge. These findings suggest that variations in the characteristics of AE are indicative of distinct micro-mechanisms active during different stages of shear localization, which cannot be fully captured by mechanical data and microstructural analysis alone.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB030448","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143707355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thank You to Our 2024 Reviewers","authors":"Alexandre Schubnel,&nbsp;Rachel Abercrombie,&nbsp;Mark D. Behn,&nbsp;Yves Bernabé,&nbsp;Mark Dekkers,&nbsp;Susanna Ebmeier,&nbsp;Anke Friedrich,&nbsp;Shin-Chan Han,&nbsp;Satoshi Ide,&nbsp;Fenglin Niu,&nbsp;Douglas R. Schmitt,&nbsp;Jun Tsuchiya","doi":"10.1029/2025JB031548","DOIUrl":"10.1029/2025JB031548","url":null,"abstract":"<p>The entire editorial board of the <i>Journal of Geophysical Research-Solid Earth</i> would like to sincerely thank all our colleagues who reviewed manuscripts for us in 2024. The hours they spent reading in order to provide insightful comments on manuscripts not only help improve the quality of these manuscripts but also ensure the scientific rigor of our reviewing process and eventually, of the research published in the field of Solid Earth Geophysics by our journal. With the advent of open science and AGU's data policy, the reviewing process now also encompasses checking the accessibility and availability of data and developed software. This is a key objective of AGU's FAIR (Findable, Accessible, Interoperable and Reusable) (FAIR) policy, for which many reviewers have provided suggestions that helped to improve the data presentation and availability, and which also fed the editorial board's reflection on the matter. Of course, we particularly appreciate timely reviews, particularly in light of the growing demands imposed by the increase of manuscripts submitted to <i>Journal of Geophysical Research-Solid Earth</i>. We received 1,999 submissions in 2024, and 1,628 reviewers contributed to their evaluation by providing 2,534 reviews in total. We are deeply thankful for all of their contributions.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JB031548","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143703505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ambient Noise Array Tomography Using Regionalized Phase Velocities From Array-Based Methods","authors":"Kaifeng Zhao,&nbsp;Yingjie Yang,&nbsp;Yinhe Luo,&nbsp;Hao Jin,&nbsp;Chengxin Jiang","doi":"10.1029/2024JB030280","DOIUrl":"https://doi.org/10.1029/2024JB030280","url":null,"abstract":"<p>With the advancement of dense seismic arrays, array-processing methods for ambient noise data have become highly effective in extracting high-quality broadband surface wave dispersion curves from ambient noise. Recent advancements in array data processing methods have enabled the extraction of multimode dispersion curves, offering improved constraints on deep Earth structures. However, these array-based methods often produce regionalized dispersion curves, and conventional phase velocity maps constructed by interpolating these dispersion curves typically have limited resolution, and display smooth images of phase velocities. In this study, we develop an array tomography method aimed at improving the resolution of ambient noise tomography by utilizing dispersion curves extracted through array-based data processing. To demonstrate the effectiveness of our method in enhancing tomography resolution, we construct fundamental-mode 2-D Rayleigh wave phase velocity maps by applying our approach to regionalized dispersion curves obtained from array-based methods in the western United States. By comparing our tomographic results with those from conventional array-based methods, we show that our method can produce more accurate and higher-resolution phase velocity maps. Additionally, our approach is versatile and can be applied to construct high-resolution 1-D and 2-D velocity structures using regionalized phase velocities obtained from various other array-based data processing methods.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143690274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismic Imaging of the Salt Lake Basin Using Joint Inversion of Receiver Functions and Rayleigh Wave Data","authors":"HyeJeong Kim,&nbsp;Fan-Chi Lin,&nbsp;James C. Pechmann,&nbsp;Christian L. Hardwick,&nbsp;Adam P. McKean","doi":"10.1029/2024JB030927","DOIUrl":"https://doi.org/10.1029/2024JB030927","url":null,"abstract":"<p>This study presents a new velocity model for the Salt Lake basin (SLB) in Utah, determined using data from permanent and temporary seismic stations located on top of the basin in the Salt Lake Valley (SLV) and nearby. A three-dimensional (3D) velocity model for the SLB is needed for accurate predictions of future damaging earthquake ground shaking in the heavily urbanized SLV, including Salt Lake City. The SLB part of the Wasatch Front community velocity model (WFCVM) currently serves this purpose. However, the current WFCVM is based primarily on gravity and borehole data with relatively few seismic constraints below depths of 100 m. In this study we use the first peak of SLV receiver functions (RFs), which is sensitive to a strong impedance contrast at the base of a semi-consolidated sediment layer. We jointly invert the RF waveform with Rayleigh wave ellipticity (H/V) and phase velocity measurements using the Markov chain Monte Carlo approach. Our new velocity model shows a greater combined thickness of unconsolidated and semi-consolidated sediments, compared to the WFCVM, in the northeastern SLB between the west-dipping East Bench fault section of the Wasatch fault and the antithetic West Valley fault zone to the west. We show that the new seismic velocity model explains the gravity patterns in the valley. The new velocity model from this study provides a basis for revising the SLB model in the WFCVM.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB030927","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143690276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Systematic Differences in Energy Radiation Processes Between Regular and Intraplate Low-Frequency Earthquakes Around the Focal Area of the 2008 \u0000 \u0000 \u0000 \u0000 M\u0000 w\u0000 \u0000 \u0000 ${boldsymbol{M}}_{boldsymbol{w}}$\u0000 6.9 Iwate-Miyagi, Japan, Earthquake","authors":"Masaki Orimo,&nbsp;Keisuke Yoshida,&nbsp;Toru Matsuzawa,&nbsp;Taka'aki Taira,&nbsp;Kentaro Emoto,&nbsp;Akira Hasegawa","doi":"10.1029/2024JB030750","DOIUrl":"10.1029/2024JB030750","url":null,"abstract":"&lt;p&gt;Many unknowns exist regarding the energy radiation processes of intraplate low-frequency earthquakes (LFEs), which are frequently observed beneath volcanoes. To evaluate their energy radiation characteristics, we estimated scaled energy (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${e}_{R}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) for LFEs and regular earthquakes around the focal area of the 2008 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;M&lt;/mi&gt;\u0000 &lt;mi&gt;w&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${M}_{w}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 6.9 Iwate-Miyagi, Japan, earthquake. Their source spectra were first obtained by correcting for the site and path effects from direct S-waves. We then estimated the radiated energy and seismic moment and obtained the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${e}_{R}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; for the 1,421 regular earthquakes, 62 deep LFEs, and 46 shallow LFEs. The &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${e}_{R}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; for the regular earthquakes is in the order of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mn&gt;10&lt;/mn&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;5&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${10}^{-5}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; to &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mn&gt;10&lt;/mn&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;4&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${10}^{-4}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, typical for crustal earthquakes and tends to be smaller near volcanoes and the shallow LFEs. In contrast, the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 ","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB030750","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143678244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trans-Crustal Geophysical Responses Beneath the Supergiant Timmins-Porcupine Orogenic Gold Camp, Canada","authors":"A. Q. Adetunji,&nbsp;I. J. Ferguson,&nbsp;J. M. Simmons,&nbsp;C. Ma,&nbsp;S. Cheraghi,&nbsp;D. B. Snyder,&nbsp;J. A. Ayer","doi":"10.1029/2024JB028839","DOIUrl":"10.1029/2024JB028839","url":null,"abstract":"<p>A new 80-site magnetotelluric (MT) survey, integrated with reprocessed seismic reflection profiles, across the supergiant Timmins-Porcupine gold camp of the Abitibi greenstone belt (AGB) was conducted to investigate the architecture of crustal-scale structures. Resistivity sections derived from 3-D MT inversions reveal a significant 600 S conductor north of the Porcupine-Destor fault zone at 3–5 km depth striking east-west parallel to the Pipestone fault zone. It is attributed to a deeply buried &gt;2687 Ma graphitic argillaceous unit at the base of Porcupine assemblage. A second conductor at 8–10 km depth strikes northwest-southeast parallel to the Buskegau River fault. The margin of this conductor correlates spatially with lateral breaks in seismic reflectors and velocity models in the upper, middle, and lower crust, and adds to evidence of a crustal-scale suture which also resulted in imbrication of &lt;2698 Ma metasedimentary rocks onto the southern AGB. Enhanced conductivity and spatially complex electrical structure of the crust to the north of the Porcupine-Destor fault zone reflect the asymmetric distribution of metasedimentary packages, second- and third-order bounding structures, and gold mineralization. The MT resistivity models also resolve an upper crustal conductor located 10 km south of the surface trace of the Porcupine-Destor fault zone, providing support for a south-dipping crustal fault. The Timmins results suggest middle crustal signatures of the extensional stage of the fault system have been overprinted by orogen-parallel ductile flow at ∼2660–2590 Ma and narrow (2–5 km wide) breaks in seismic reflectors are more likely associated with late strike-slip deformation.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB028839","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143675517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New Paleomagnetic Constraints on the Eruption Timing, Stratigraphy, and Post-Emplacement Deformation of the Picture Gorge Basalt Within the Columbia River Basalt Group","authors":"A. F. Pivarunas,&nbsp;M. S. Avery,&nbsp;J. T. Hagstrum,&nbsp;S. E. K. Bennett,&nbsp;A. T. Calvert","doi":"10.1029/2024JB030728","DOIUrl":"10.1029/2024JB030728","url":null,"abstract":"<p>The Picture Gorge Basalt (PGB) is part of the Miocene Columbia River Basalt Group (CRBG). The PGB, which outcrops in eastern Oregon, is considered coincident in time with the voluminous Grande Ronde Basalt. New radiometric ages have expanded the age-range of the PGB, suggesting it began erupting prior to the Steens Basalt to its south and continued until after cessation of the Grande Ronde Basalt eruptions, an interval of 1.5 Ma. However, the existing paleomagnetism of the PGB implies this eruption timeline is an overestimate. To reconcile the radiometric and paleomagnetic timescales for the PGB, we conducted a paleomagnetic study on sections of the PGB to construct a detailed, high-quality magnetostratigraphy. Our data indicate the stratigraphically lowest lava flows in the PGB are of reversed polarity, revealing a new paleomagnetic transition with the PGB and a reversed (R)–normal (N)–reversed (R) sequence. This suggests one of two timeline possibilities for PGB volcanism: (a) eruptions began and during through CRBG polarity chrons R0–N0–R1, penecontemporaneous with Steens Basalt, or (b) eruptions began and persisted during CRBG polarity chrons R1–N1–R2. Our work supports a longer interval of PGB volcanism than was suggested by previous paleomagnetic data but is at odds with the suggestion that PGB eruptions lasted through the entire main CRBG. We favor a scenario wherein PGB eruptions begin with R0 and continue into the R1 paleomagnetic interval. The paleomagnetic results also record a ∼18° vertical-axis rotation of east-central Oregon after ∼16 Ma with respect to stable North America.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143675516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"b-Bayesian: The Full Probabilistic Estimate of b-Value Temporal Variations for Non-Truncated Catalogs","authors":"M. Laporte,&nbsp;S. Durand,&nbsp;T. Bodin,&nbsp;B. Gardonio,&nbsp;D. Marsan","doi":"10.1029/2024JB029973","DOIUrl":"10.1029/2024JB029973","url":null,"abstract":"&lt;p&gt;The frequency/magnitude distribution of earthquakes can be approximated by an exponential law whose exponent (the so-called &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;b&lt;/mi&gt;\u0000 &lt;mi&gt;value&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${b}_{mathit{value}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) is routinely used for probabilistic seismic hazard assessment. The &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;b&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;v&lt;/mi&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;mi&gt;l&lt;/mi&gt;\u0000 &lt;mi&gt;u&lt;/mi&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${b}_{value}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; is commonly measured using Aki's maximum likelihood estimation, although biases can arise from the choice of completeness magnitude (i.e., the magnitude below which the exponential law is no longer valid). In this work, we introduce the b-Bayesian method, where the full frequency-magnitude distribution of earthquakes is modeled by the product of an exponential law and a detection law. The detection law is characterized by two parameters, which we jointly estimate with the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;b&lt;/mi&gt;\u0000 &lt;mi&gt;value&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${b}_{mathit{value}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; within a Bayesian framework. All available data are used to recover the joint probability distribution. The b-Bayesian approach recovers temporal variations of the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;b&lt;/mi&gt;\u0000 &lt;mi&gt;value&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${b}_{mathit{value}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and the detectability using a transdimensional Markov-chain Monte Carlo algorithm to explore numerous configurations of their time variations. An application to a seismic catalog of far-western Nepal shows that detectability decreases significantly during the monsoon period, while the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;b&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;v&lt;/mi&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;mi&gt;l&lt;/mi&gt;\u0000 &lt;mi&gt;u&lt;/mi&gt;\u0000 &lt;mi&gt;e&lt;/","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029973","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143672694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}