DBSCAN is a widely used unsupervised machine learning algorithm for clustering and spatial data analysis. However, the accuracy of the algorithm is highly dependent on the selection of its hyperparameters, minimum samples (Smin), the minimum number of points required to form a cluster, and ϵ, the maximum distance between points. In this study, we propose a modification to the DBSCAN algorithm by introducing an event density map replacing Smin and ε. Through this method, we decrease the number of hyperparameters from two to one, N which represents the number of cells in the event density map, simplifying, and speeding up optimization. As a result, the optimization of the algorithm will be improved as the sole factor to consider is the size of each cell. In addition, the utilization of dynamic Smin will provide more effective clustering because it is better suited to regions that have a variable earthquake density. We used the Iranian earthquake catalog for testing the algorithm, and we compared the outcomes to the Mirzaei et al. (1998) model as a standard for evaluation. Because this algorithm allows for density contrasts between clusters, it can be a good indicator when studying the zonation of a new area. The findings were more consistent than those of other methods and may offer additional insight into the seismotectonic of Iran. Other than earthquake studies, this algorithm can be applied in multiple fields of science and engineering for clustering datasets with variable-density clusters.
DBSCAN是一种广泛应用于聚类和空间数据分析的无监督机器学习算法。然而，该算法的准确性高度依赖于其超参数的选择，最小样本(Smin)，形成聚类所需的最小点数，以及点之间的最大距离。在这项研究中，我们提出了一种改进的DBSCAN算法，通过引入一个事件密度图来取代Smin和ε。通过该方法，我们将超参数的数量从2个减少到1个，N代表事件密度图中的单元数，简化了优化过程，加快了优化速度。因此，算法的优化将得到改善，因为唯一要考虑的因素是每个单元的大小。此外，动态Smin的利用将提供更有效的聚类，因为它更适合具有可变地震密度的地区。我们使用伊朗地震目录来测试算法，并将结果与Mirzaei et al.(1998)模型作为评估标准进行了比较。由于该算法允许集群之间的密度对比，因此在研究新区域的分区时，它可以成为一个很好的指标。这些发现比其他方法更加一致，并可能为了解伊朗的地震构造提供额外的见解。除地震研究外，该算法还可以应用于科学和工程的多个领域，用于变密度聚类的数据集聚类。
{"title":"Improved Earthquake Clustering Using a Density-Adaptive DBSCAN Algorithm: An Example from Iran","authors":"Sina Sabermahani, Andrew W. Frederiksen","doi":"10.1785/0220220305","DOIUrl":"https://doi.org/10.1785/0220220305","url":null,"abstract":"\u0000 DBSCAN is a widely used unsupervised machine learning algorithm for clustering and spatial data analysis. However, the accuracy of the algorithm is highly dependent on the selection of its hyperparameters, minimum samples (Smin), the minimum number of points required to form a cluster, and ϵ, the maximum distance between points. In this study, we propose a modification to the DBSCAN algorithm by introducing an event density map replacing Smin and ε. Through this method, we decrease the number of hyperparameters from two to one, N which represents the number of cells in the event density map, simplifying, and speeding up optimization. As a result, the optimization of the algorithm will be improved as the sole factor to consider is the size of each cell. In addition, the utilization of dynamic Smin will provide more effective clustering because it is better suited to regions that have a variable earthquake density. We used the Iranian earthquake catalog for testing the algorithm, and we compared the outcomes to the Mirzaei et al. (1998) model as a standard for evaluation. Because this algorithm allows for density contrasts between clusters, it can be a good indicator when studying the zonation of a new area. The findings were more consistent than those of other methods and may offer additional insight into the seismotectonic of Iran. Other than earthquake studies, this algorithm can be applied in multiple fields of science and engineering for clustering datasets with variable-density clusters.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138595697","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":"Erratum to An Evaluation of the Timing Accuracy of Global and Regional Seismic Stations and Networks","authors":"Yi Yang, Xiaodong Song, A. Ringler","doi":"10.1785/0220230360","DOIUrl":"https://doi.org/10.1785/0220230360","url":null,"abstract":"","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138597918","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}
Nicolas Leroy, Martin Vallée, D. Zigone, Barbara Romanowicz, É. Stutzmann, Alessia Maggi, C. Pardo, J. Montagner, M. Bès de Berc, C. Broucke, S. Bonaimé, Geneviève Roult, J. Thore, Armelle Bernard, Michel Le Cocq, O. Sirol, Luis Rivera, J. Lévêque, Michel Cara, Frédérick Pesqueira
The GEOSCOPE observatory (Institut de physique du globe de Paris [IPGP] and École et Observatoire des Sciences de la Terre de Strasbourg, 1982) provides more than four decades of high-quality continuous broadband data to the scientific community. Started in 1982 with only two stations, the network has grown over the years thanks to numerous international partnerships. At present, 34 stations operate in 18 countries across all continents and on islands throughout the oceans, filling important gaps in global Earth coverage. Most of the first installed stations are still running today, allowing for long-term observations, and new sites are being prospected to further improve global coverage. Over the years, GEOSCOPE has contributed to defining today’s global seismology standards (data format, data quality level, instrumentation requirements), being the French contribution to the international effort for global seismic observations. The stations are instrumented with the best quality seismometers (from the very first STS-1 in the early 80s to the last STS-6A and Trillium T360 today) and digitizers (Q330HR and Centaur) to record with high fidelity the ground motions generated by all types of seismic sources. Real-time data are sent to the tsunami warning centers and both validated and real-time data are available at the IPGP, Epos-France and Earthscope data centers. The quality of GEOSCOPE data and metadata is ensured by daily and yearly validation that enables issue detection and mitigation. GEOSCOPE, in collaboration with the other global networks, has played and continues to play a crucial role in the study of Earth’s structure and global dynamics and the characterization of all types of seismic sources.
GEOSCOPE天文台(巴黎地球物理研究所[IPGP]和École et Observatoire des Sciences de la Terre de Strasbourg, 1982年)为科学界提供了40多年的高质量连续宽带数据。1982年开始时只有两个电台，由于众多的国际合作伙伴关系，该网络多年来不断发展壮大。目前，34个台站在各大洲的18个国家和各大洋的岛屿上开展业务，填补了全球地球覆盖的重要空白。大多数第一批安装的站点今天仍在运行，可以进行长期观测，并且正在寻找新的站点以进一步改善全球覆盖范围。多年来，GEOSCOPE为定义当今的全球地震学标准(数据格式，数据质量水平，仪器要求)做出了贡献，这是法国对全球地震观测国际努力的贡献。这些台站配备了最优质的地震仪(从80年代初的第一个STS-1到今天的最后一个STS-6A和Trillium T360)和数字化仪(Q330HR和Centaur)，以高保真度记录所有类型震源产生的地面运动。实时数据被发送到海啸预警中心，IPGP、Epos-France和Earthscope数据中心都可以获得验证数据和实时数据。GEOSCOPE数据和元数据的质量通过每日和每年的验证得到保证，从而能够发现和缓解问题。GEOSCOPE与其他全球网络合作，在研究地球结构和全球动力学以及所有类型震源的特征方面已经并将继续发挥关键作用。
{"title":"GEOSCOPE Network: 40 Yr of Global Broadband Seismic Data","authors":"Nicolas Leroy, Martin Vallée, D. Zigone, Barbara Romanowicz, É. Stutzmann, Alessia Maggi, C. Pardo, J. Montagner, M. Bès de Berc, C. Broucke, S. Bonaimé, Geneviève Roult, J. Thore, Armelle Bernard, Michel Le Cocq, O. Sirol, Luis Rivera, J. Lévêque, Michel Cara, Frédérick Pesqueira","doi":"10.1785/0220230176","DOIUrl":"https://doi.org/10.1785/0220230176","url":null,"abstract":"\u0000 The GEOSCOPE observatory (Institut de physique du globe de Paris [IPGP] and École et Observatoire des Sciences de la Terre de Strasbourg, 1982) provides more than four decades of high-quality continuous broadband data to the scientific community. Started in 1982 with only two stations, the network has grown over the years thanks to numerous international partnerships. At present, 34 stations operate in 18 countries across all continents and on islands throughout the oceans, filling important gaps in global Earth coverage. Most of the first installed stations are still running today, allowing for long-term observations, and new sites are being prospected to further improve global coverage. Over the years, GEOSCOPE has contributed to defining today’s global seismology standards (data format, data quality level, instrumentation requirements), being the French contribution to the international effort for global seismic observations. The stations are instrumented with the best quality seismometers (from the very first STS-1 in the early 80s to the last STS-6A and Trillium T360 today) and digitizers (Q330HR and Centaur) to record with high fidelity the ground motions generated by all types of seismic sources. Real-time data are sent to the tsunami warning centers and both validated and real-time data are available at the IPGP, Epos-France and Earthscope data centers. The quality of GEOSCOPE data and metadata is ensured by daily and yearly validation that enables issue detection and mitigation. GEOSCOPE, in collaboration with the other global networks, has played and continues to play a crucial role in the study of Earth’s structure and global dynamics and the characterization of all types of seismic sources.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138605099","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}
The Querétaro region (central Mexico) is located in the trans-Mexican volcanic belt, an active volcanic arc related to the subduction of oceanic plates along the Pacific margin of Mexico. It is characterized by north–south-striking normal faults of the southern Basin and Range Province, up to 40 km long and with morphologically pronounced scarps, such as the San Miguel de Allende fault and the faults forming the Querétaro graben. These faults are located directly north of a major regional-scale system of east–west striking, seismically active intra-arc normal faults that are oriented parallel to the axis of the volcanic arc. Where the two orthogonal normal fault systems interfere, the outcrop-scale observations show that the east–west intra-arc fault system overprints the Basin and Range Province structures. Here we document a 1934 earthquake in a region previously not known for seismic activity. Our study is mostly based on an unpublished contemporary dossier preserved at Archivo Histórico del Instituto de Geología de la Universidad Nacional Autónoma de México, a recently inventoried archive that also preserves several unpublished macroseismic and instrumental studies of major Mexican subduction zone earthquakes between 1911 and 1954. A mainshock–aftershock sequence that initiated 14 July 1934 is documented by instrumental recordings at the Tacubaya observatory and by macroseismic observations at ten population centers, ranging in intensity between five and seven on the modified Mercalli scale. Based on the size of the damage area, the intensity magnitude of the mainshock is estimated at 4.8 ± 0.5. Based on the intensity distribution, the epicenter was located in the Laja River valley north-northeast of the town of Celaya, in the south-southwestern extrapolated continuation of the San Miguel de Allende normal fault scarp, which suggests that this fault extends to the epicentral region of the 1934 earthquake and is characterized by recurrent Quaternary tectonic activity.
querimataro地区(墨西哥中部)位于跨墨西哥火山带，这是一条与墨西哥太平洋边缘海洋板块俯冲有关的活火山弧。它的特征是南部盆地和山脉省的南北走向的正断层，长达40公里，具有形态明显的陡崖，如圣米格尔德阿连德断层和形成querimadaro地堑的断层。这些断层位于与火山弧轴线平行的东西向、地震活跃的弧内正断层的主要区域尺度系统的正北。露头尺度观测显示，东西向的弧内断裂体系覆盖了盆地和岭省构造。在这里，我们记录了1934年在一个以前不知道地震活动的地区发生的地震。我们的研究主要基于保存在档案馆Histórico del Instituto de Geología de la Universidad Nacional Autónoma de macimxico的一份未发表的当代档案，这是一份最近编录的档案，其中还保存了一些未发表的关于1911年至1954年墨西哥俯冲带主要地震的宏观地震和仪器研究。塔库巴亚天文台的仪器记录和10个人口中心的宏观地震观测记录了始于1934年7月14日的主震-余震序列，强度在修正的Mercalli震级5到7级之间。根据震区大小，估计主震烈度为4.8±0.5级。根据地震强度分布，震中位于Celaya镇东北偏北的Laja河流域，位于San Miguel de Allende正断层断崖的西南向外推延续性中，表明该断层延伸至1934年地震的震中区域，具有第四纪构造活动频繁的特征。
{"title":"Seismotectonics of the Querétaro Region (Central Mexico) and the 1934 MI 4.8 Earthquake North of Celaya","authors":"Max Suter, Lucero Morelos-Rodríguez","doi":"10.1785/0220230256","DOIUrl":"https://doi.org/10.1785/0220230256","url":null,"abstract":"\u0000 The Querétaro region (central Mexico) is located in the trans-Mexican volcanic belt, an active volcanic arc related to the subduction of oceanic plates along the Pacific margin of Mexico. It is characterized by north–south-striking normal faults of the southern Basin and Range Province, up to 40 km long and with morphologically pronounced scarps, such as the San Miguel de Allende fault and the faults forming the Querétaro graben. These faults are located directly north of a major regional-scale system of east–west striking, seismically active intra-arc normal faults that are oriented parallel to the axis of the volcanic arc. Where the two orthogonal normal fault systems interfere, the outcrop-scale observations show that the east–west intra-arc fault system overprints the Basin and Range Province structures. Here we document a 1934 earthquake in a region previously not known for seismic activity. Our study is mostly based on an unpublished contemporary dossier preserved at Archivo Histórico del Instituto de Geología de la Universidad Nacional Autónoma de México, a recently inventoried archive that also preserves several unpublished macroseismic and instrumental studies of major Mexican subduction zone earthquakes between 1911 and 1954. A mainshock–aftershock sequence that initiated 14 July 1934 is documented by instrumental recordings at the Tacubaya observatory and by macroseismic observations at ten population centers, ranging in intensity between five and seven on the modified Mercalli scale. Based on the size of the damage area, the intensity magnitude of the mainshock is estimated at 4.8 ± 0.5. Based on the intensity distribution, the epicenter was located in the Laja River valley north-northeast of the town of Celaya, in the south-southwestern extrapolated continuation of the San Miguel de Allende normal fault scarp, which suggests that this fault extends to the epicentral region of the 1934 earthquake and is characterized by recurrent Quaternary tectonic activity.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138602537","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}
Historical seismic catalogs of Italy record several instances of pairs or triplets of large earthquakes (Mw>6.7) along the Apennine chain, occurring on the same date or within a short time frame (days or weeks). Some of these events have mesoseismic areas tens of kilometers apart and/or seismogenic structures located more than 1–3 times the fault length away. Although in the case of aligned and/or contiguous faults, their cascading activation can be explained by variations in static Coulomb stress, in the case of distant faults, this mechanism could sometimes be replaced by what is known as dynamic triggering, which is caused by the passage of seismic waves generated by a remote source. In this study, I analyze three significant ancient seismic sequences that occurred in the south-central Apennines, suggesting that the extent of the destructive effects of these earthquakes can be attributed to remote dynamic triggering, causing the activation of different and unrelated seismogenic structures within a specific time frame.
{"title":"Nearly Simultaneous Pairs and Triplets of Historical Destructive Earthquakes with Distant Epicenters in the Italian Apennines","authors":"Paolo Galli","doi":"10.1785/0220230135","DOIUrl":"https://doi.org/10.1785/0220230135","url":null,"abstract":"\u0000 Historical seismic catalogs of Italy record several instances of pairs or triplets of large earthquakes (Mw>6.7) along the Apennine chain, occurring on the same date or within a short time frame (days or weeks). Some of these events have mesoseismic areas tens of kilometers apart and/or seismogenic structures located more than 1–3 times the fault length away. Although in the case of aligned and/or contiguous faults, their cascading activation can be explained by variations in static Coulomb stress, in the case of distant faults, this mechanism could sometimes be replaced by what is known as dynamic triggering, which is caused by the passage of seismic waves generated by a remote source. In this study, I analyze three significant ancient seismic sequences that occurred in the south-central Apennines, suggesting that the extent of the destructive effects of these earthquakes can be attributed to remote dynamic triggering, causing the activation of different and unrelated seismogenic structures within a specific time frame.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138604538","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}
É. Beaucé, W. Frank, L. Seydoux, Piero Poli, Nathan Groebner, R. D. van der Hilst, Michel Campillo
We introduce BPMF (backprojection and matched filtering)—a complete and fully automated workflow designed for earthquake detection and location, and distributed in a Python package. This workflow enables the creation of comprehensive earthquake catalogs with low magnitudes of completeness using no or little prior knowledge of the study region. BPMF uses the seismic wavefield backprojection method to construct an initial earthquake catalog that is then densified with matched filtering. BPMF integrates recent machine learning tools to complement physics-based techniques, and improve the detection and location of earthquakes. In particular, BPMF offers a flexible framework in which machine learning detectors and backprojection can be harmoniously combined, effectively transforming single-station detectors into multistation detectors. The modularity of BPMF grants users the ability to control the contribution of machine learning tools within the workflow. The computation-intensive tasks (backprojection and matched filtering) are executed with C and CUDA-C routines wrapped in Python code. This leveraging of low-level, fast programming languages and graphic processing unit acceleration enables BPMF to efficiently handle large datasets. Here, we first summarize the methodology and describe the application programming interface. We then illustrate BPMF’s capabilities to characterize microseismicity with a 10 yr long application in the Ridgecrest, California area. Finally, we discuss the workflow’s runtime scaling with numerical resources and its versatility across various tectonic environments and different problems.
{"title":"BPMF: A Backprojection and Matched-Filtering Workflow for Automated Earthquake Detection and Location","authors":"É. Beaucé, W. Frank, L. Seydoux, Piero Poli, Nathan Groebner, R. D. van der Hilst, Michel Campillo","doi":"10.1785/0220230230","DOIUrl":"https://doi.org/10.1785/0220230230","url":null,"abstract":"\u0000 We introduce BPMF (backprojection and matched filtering)—a complete and fully automated workflow designed for earthquake detection and location, and distributed in a Python package. This workflow enables the creation of comprehensive earthquake catalogs with low magnitudes of completeness using no or little prior knowledge of the study region. BPMF uses the seismic wavefield backprojection method to construct an initial earthquake catalog that is then densified with matched filtering. BPMF integrates recent machine learning tools to complement physics-based techniques, and improve the detection and location of earthquakes. In particular, BPMF offers a flexible framework in which machine learning detectors and backprojection can be harmoniously combined, effectively transforming single-station detectors into multistation detectors. The modularity of BPMF grants users the ability to control the contribution of machine learning tools within the workflow. The computation-intensive tasks (backprojection and matched filtering) are executed with C and CUDA-C routines wrapped in Python code. This leveraging of low-level, fast programming languages and graphic processing unit acceleration enables BPMF to efficiently handle large datasets. Here, we first summarize the methodology and describe the application programming interface. We then illustrate BPMF’s capabilities to characterize microseismicity with a 10 yr long application in the Ridgecrest, California area. Finally, we discuss the workflow’s runtime scaling with numerical resources and its versatility across various tectonic environments and different problems.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138602673","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}
Based on the advantages of the chaos particle swarm optimization algorithm and the generalized inversion technology, this article estimates the source parameters and site effects of the Wenchuan earthquake. We used 440 sets of strong-motion records obtained from 43 aftershocks, and the area covered by the records was divided into subregions A and B. Initial separation of source, path, and site from the seismic spectra of subregions A and B using generalized inversion technique and then the source-site optimization model is established using chaotic particle swarm technology. From path-corrected records, we obtained absolute site effects for 33 stations and equivalent source parameters for 43 earthquakes. We made the following conclusions: (1) The moment magnitude Mw was lower than the local magnitude MLdetermined by China Earthquake Network Center. The self-similarity of the Wenchuan earthquake was confirmed. The stress drop averaged 2.31 MPa, and it was independent of the magnitude size and focal depth. (2) In the frequency 1–10 Hz, the quality factor values in subregions A and B are 110.9f0.6 and 116.1f1.2. The decay rate of the crustal medium in the western region of the west Sichuan plateau is significant compared to the eastern part. (3) Bedrock stations 51MXT and L2007 have site effects within a certain frequency. The effect of slope topography on site predominant frequency is not apparent, and the site effects increase with the increase in elevation. The shape of the site amplification curve is more similar in the middle- and low-frequency bands, and different attenuation phenomena will appear in the high-frequency band.
{"title":"Estimation of Site Effects and Equivalent Source Parameters of Wenchuan Earthquake Based on Generalized Chaotic Particle Inversion Technique","authors":"Ke-Lin Chen, Xue-Liang Chen, Jingyan Lan, Li-Jun Qiu, Yi-Ling Zhu","doi":"10.1785/0220230028","DOIUrl":"https://doi.org/10.1785/0220230028","url":null,"abstract":"Based on the advantages of the chaos particle swarm optimization algorithm and the generalized inversion technology, this article estimates the source parameters and site effects of the Wenchuan earthquake. We used 440 sets of strong-motion records obtained from 43 aftershocks, and the area covered by the records was divided into subregions A and B. Initial separation of source, path, and site from the seismic spectra of subregions A and B using generalized inversion technique and then the source-site optimization model is established using chaotic particle swarm technology. From path-corrected records, we obtained absolute site effects for 33 stations and equivalent source parameters for 43 earthquakes. We made the following conclusions: (1) The moment magnitude Mw was lower than the local magnitude MLdetermined by China Earthquake Network Center. The self-similarity of the Wenchuan earthquake was confirmed. The stress drop averaged 2.31 MPa, and it was independent of the magnitude size and focal depth. (2) In the frequency 1–10 Hz, the quality factor values in subregions A and B are 110.9f0.6 and 116.1f1.2. The decay rate of the crustal medium in the western region of the west Sichuan plateau is significant compared to the eastern part. (3) Bedrock stations 51MXT and L2007 have site effects within a certain frequency. The effect of slope topography on site predominant frequency is not apparent, and the site effects increase with the increase in elevation. The shape of the site amplification curve is more similar in the middle- and low-frequency bands, and different attenuation phenomena will appear in the high-frequency band.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139202592","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}
Sepideh J. Rastin, D. Rhoades, Chris Rollins, Matthew C. Gerstenberger
We propose a method to estimate the uncertainty of the average rate of earthquakes exceeding a magnitude threshold in a future period of given length based on observed variability of the earthquake process in an existing catalog. We estimate the ratio R of the variability to that of a stationary Poisson process. R is estimated from subsets of the catalog over a wide range of timescales. The method combines the epistemic uncertainty in estimating the rate from the catalog and the aleatory variability of the rate in future time periods. If R is stable over many timescales, there is a solid basis for estimating the uncertainty of earthquake rate estimates. In the 2022 revision of the New Zealand National Seismic Hazard Model (NZ NSHM), estimation of the total shallow earthquake rate over the next 100 yr and its uncertainty is an important element. Using a 70 yr New Zealand catalog with hypocentral depths ≤40 km and standardized magnitudes M ≥ 4.95, we find stable estimates of R for timescales from 3 days to 2.4 yr. This gives a standard error of 0.95 on the estimated annual rate of M ≥ 4.95, in the next 100 yr. R becomes unstable and has poor precision for longer subperiods. We investigate potential causes using synthetic catalogs with known inhomogeneities. Analysis of International Seismological Centre-Global Earthquake Model (ISC-GEM) catalog, to investigate the effect of higher magnitude thresholds, shows that R is lower for M ≥ 6.95 than for M ≥ 5.45. The ISC-GEM catalog restricted to New Zealand gives comparable stable estimates of R to the NZ NSHM 2022 catalog for M ≥ 5.45 and lower estimates than the NZ NSHM 2022 catalog for M ≥ 4.95. We also verify that magnitude standardization of the New Zealand GeoNet catalog has reduced the uncertainty of rate estimates by decreasing R throughout the entire range of timescales.
我们提出了一种方法，可以根据现有目录中观测到的地震过程的变异性，估算在未来给定长度的时期内超过震级阈值的地震平均发生率的不确定性。我们估算的是变异性与静止泊松过程的比率 R。R 是在广泛的时间尺度范围内根据目录子集估算出来的。该方法结合了从目录中估算比率的认识不确定性和未来时间段内比率的已知变异性。如果 R 在许多时间尺度上是稳定的，那么估算地震发生率估计值的不确定性就有了坚实的基础。在 2022 年对新西兰国家地震危险性模型（NZ NSHM）的修订中，估算未来 100 年的总浅层地震率及其不确定性是一项重要内容。使用新西兰 70 年的地震目录，低中心深度≤40 千米，标准化震级 M ≥4.95，我们发现在 3 天到 2.4 年的时间尺度内，R 的估计值比较稳定。对于更长的子周期，R 值变得不稳定，精度也很低。我们利用已知不均匀性的合成目录研究了潜在的原因。对国际地震中心-全球地震模型（ISC-GEM）震级目录的分析表明，M ≥ 6.95 时的 R 值低于 M ≥ 5.45 时的 R 值。局限于新西兰的ISC-GEM星表对M≥5.45的R的稳定估计值与NZ NSHM 2022星表相当，而对M≥4.95的R的估计值低于NZ NSHM 2022星表。我们还验证了新西兰 GeoNet 星表的震级标准化通过在整个时间尺度范围内降低 R 来减少速率估计值的不确定性。
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D. Wilson, C. R. Hutt, L. Gee, A. Ringler, R. Anthony
The U.S. Geological Survey (USGS) Global Seismographic Network (GSN) Program operates two thirds of the GSN, a network of state-of-the-art, digital seismological and geophysical sensors with digital telecommunications. This network serves as a multiuse scientific facility and a valuable resource for research, education, and monitoring. The other one third of the GSN is funded by the National Science Foundation (NSF), and the operations of this component are overseen by EarthScope. This collaboration between the USGS, EarthScope, and NSF has allowed for the development and operations of the GSN to be a truly multiuse network that provides near real-time open access data, facilitating fundamental discoveries by the Earth science community, supporting the earthquake hazards mission of the USGS, benefitting tsunami monitoring by the National Oceanic and Atmospheric Administration, and contributing to nuclear test monitoring and treaty verification. In this article, we describe the installation and evolution of the seismic networks operated by the USGS that ultimately led to the USGS portion of the GSN (100 stations under network codes IU, IC, and CU) as they are today and envision technological advances and opportunities to further improve the utility of the network in the future. This article focuses on the USGS-operated component of the GSN; a companion article on the GSN stations funded by the NSF and operated by the Cecil and Ida Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California at San Diego by Davis et al. (2023) appears in this volume.
美国地质调查局（USGS）的全球地震网络（GSN）计划运营着三分之二的全球地震网络，这是一个由最先进的数字地震和地球物理传感器以及数字通信组成的网络。该网络是一个多用途科学设施，也是研究、教育和监测的宝贵资源。全球地震台网的另外三分之一由美国国家科学基金会（NSF）资助，该部分的运行由地球观测站（EarthScope）负责监督。美国地质调查局、EarthScope 和美国国家科学基金会之间的合作使全球海洋观测网的开发和运行成为一个真正的多用途网络，提供近乎实时的开放数据，促进地球科学界的基础发现，支持美国地质调查局的地震灾害任务，有利于美国国家海洋和大气管理局的海啸监测，并有助于核试验监测和条约验证。在本文中，我们将介绍由美国地质调查局运营的地震台网的安装和演变过程，最终形成了今天的全球地震台网美国地质调查局部分（100 个台站，台网代码分别为 IU、IC 和 CU），并展望了未来进一步提高台网效用的技术进步和机遇。本文重点介绍全球海洋观测网中由美国地质调查局运营的部分；本卷还将刊载 Davis 等人（2023 年）撰写的关于由美国国家科学基金会资助、由加州大学圣地亚哥分校斯克里普斯海洋学研究所塞西尔和艾达-格林地球物理与行星物理研究所运营的全球海洋观测网台站的文章。
{"title":"Global Seismic Networks Operated by the U.S. Geological Survey","authors":"D. Wilson, C. R. Hutt, L. Gee, A. Ringler, R. Anthony","doi":"10.1785/0220230178","DOIUrl":"https://doi.org/10.1785/0220230178","url":null,"abstract":"The U.S. Geological Survey (USGS) Global Seismographic Network (GSN) Program operates two thirds of the GSN, a network of state-of-the-art, digital seismological and geophysical sensors with digital telecommunications. This network serves as a multiuse scientific facility and a valuable resource for research, education, and monitoring. The other one third of the GSN is funded by the National Science Foundation (NSF), and the operations of this component are overseen by EarthScope. This collaboration between the USGS, EarthScope, and NSF has allowed for the development and operations of the GSN to be a truly multiuse network that provides near real-time open access data, facilitating fundamental discoveries by the Earth science community, supporting the earthquake hazards mission of the USGS, benefitting tsunami monitoring by the National Oceanic and Atmospheric Administration, and contributing to nuclear test monitoring and treaty verification. In this article, we describe the installation and evolution of the seismic networks operated by the USGS that ultimately led to the USGS portion of the GSN (100 stations under network codes IU, IC, and CU) as they are today and envision technological advances and opportunities to further improve the utility of the network in the future. This article focuses on the USGS-operated component of the GSN; a companion article on the GSN stations funded by the NSF and operated by the Cecil and Ida Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California at San Diego by Davis et al. (2023) appears in this volume.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139211206","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}
The 6 February 2023 Türkiye earthquake doublet occurred on the east Anatolian fault system, which marks the tectonic boundary between the Arabia plate and the Anatolian microplate. This earthquake doublet consists of the Mw 7.8 Pazarcik earthquake along the east Anatolian fault and the Mw 7.6 Çardak earthquake along the Savrun–Çardak fault. Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) satellite successfully imaged the surface deformation caused by this earthquake doublet. The pixel offset from cross correlation of two Synthetic Aperture Radar images complements the interferograms in mapping the surface ruptures and the near-field deformation. We inverted for a coseismic slip model in elastic half-space using the InSAR phase and the range offset data. The variance reduction of the inversion reaches ∼90%. The coseismic slip model shows that the 2023 Türkiye earthquake doublet are left-lateral strike-slip events. The peak slip is located near Nurhak in southern Türkiye along the Savrun–Çardak fault. From measuring discontinuities in the pixel offset images we found that the surface rupture length of the Pazarcik earthquake is ∼300 km and the surface rupture length of the Çardak earthquake is ∼100 km. To first order, the faults are dipping vertically. “Slip gaps” are identified by our modeling, and they might be the source regions of future large earthquakes.
{"title":"Coseismic Deformation of the 2023 Türkiye Earthquake Doublet from Sentinel-1 InSAR and Implications for Earthquake Hazard","authors":"Xiaopeng Tong, Yongzhe Wang, Shi Chen","doi":"10.1785/0220230282","DOIUrl":"https://doi.org/10.1785/0220230282","url":null,"abstract":"The 6 February 2023 Türkiye earthquake doublet occurred on the east Anatolian fault system, which marks the tectonic boundary between the Arabia plate and the Anatolian microplate. This earthquake doublet consists of the Mw 7.8 Pazarcik earthquake along the east Anatolian fault and the Mw 7.6 Çardak earthquake along the Savrun–Çardak fault. Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) satellite successfully imaged the surface deformation caused by this earthquake doublet. The pixel offset from cross correlation of two Synthetic Aperture Radar images complements the interferograms in mapping the surface ruptures and the near-field deformation. We inverted for a coseismic slip model in elastic half-space using the InSAR phase and the range offset data. The variance reduction of the inversion reaches ∼90%. The coseismic slip model shows that the 2023 Türkiye earthquake doublet are left-lateral strike-slip events. The peak slip is located near Nurhak in southern Türkiye along the Savrun–Çardak fault. From measuring discontinuities in the pixel offset images we found that the surface rupture length of the Pazarcik earthquake is ∼300 km and the surface rupture length of the Çardak earthquake is ∼100 km. To first order, the faults are dipping vertically. “Slip gaps” are identified by our modeling, and they might be the source regions of future large earthquakes.","PeriodicalId":21687,"journal":{"name":"Seismological Research Letters","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139214762","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}
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