T. Hudson, T. Kettlety, J. Kendall, Tom O’Toole, A. Jupe, Robin K. Shail, Augusta Grand
Harnessing geothermal energy will likely play a critical role in reducing global CO2 emissions. However, exploration, development, and monitoring of geothermal systems remain challenging. Here, we explore how recent low-cost seismic node instrumentation advances might enhance geothermal exploration and monitoring. We show the results from 450 nodes deployed at a geothermal prospect in Cornwall, United Kingdom. First, we demonstrate how the nodes can be used to monitor the spatiotemporal and size distribution of induced seismicity. Second, we use focal mechanisms, shear-wave source polarities, and anisotropy to indicate how the dense passive seismic observations might provide enhanced insight into the stress state of the geothermal systems. All the methods are fully automated, essential for processing the data from many receivers. In our example case study, we find that the injection-site fracture orientations significantly differ from that of the crust above and the regional stress state. These observations agree well with fracture orientations inferred from independent well-log data, exemplifying how the nodes can provide new insight for understanding the geothermal systems. Finally, we discuss the limitations of nodes and the role they might play in hybrid seismic monitoring going forward. Overall, our results emphasize the important role that low-cost, easy-to-deploy dense nodal arrays can play in geothermal exploration and operation.
{"title":"Seismic Node Arrays for Enhanced Understanding and Monitoring of Geothermal Systems","authors":"T. Hudson, T. Kettlety, J. Kendall, Tom O’Toole, A. Jupe, Robin K. Shail, Augusta Grand","doi":"10.1785/0320240019","DOIUrl":"https://doi.org/10.1785/0320240019","url":null,"abstract":"\u0000 Harnessing geothermal energy will likely play a critical role in reducing global CO2 emissions. However, exploration, development, and monitoring of geothermal systems remain challenging. Here, we explore how recent low-cost seismic node instrumentation advances might enhance geothermal exploration and monitoring. We show the results from 450 nodes deployed at a geothermal prospect in Cornwall, United Kingdom. First, we demonstrate how the nodes can be used to monitor the spatiotemporal and size distribution of induced seismicity. Second, we use focal mechanisms, shear-wave source polarities, and anisotropy to indicate how the dense passive seismic observations might provide enhanced insight into the stress state of the geothermal systems. All the methods are fully automated, essential for processing the data from many receivers. In our example case study, we find that the injection-site fracture orientations significantly differ from that of the crust above and the regional stress state. These observations agree well with fracture orientations inferred from independent well-log data, exemplifying how the nodes can provide new insight for understanding the geothermal systems. Finally, we discuss the limitations of nodes and the role they might play in hybrid seismic monitoring going forward. Overall, our results emphasize the important role that low-cost, easy-to-deploy dense nodal arrays can play in geothermal exploration and operation.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":"52 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141842975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Seismic wave attenuation and the related shear-wave quality factor (QS) in the near surface are crucial parameters for ground motion simulations and seismic hazard assessments. Although recent approaches developed to calculate QS from seismic noise acquired by surface arrays have been accepted for practice, additional testing and comparison of results estimated using various geophysical methods are still necessary to verify the reliability of such techniques. This work presents the results of an experiment conducted at the STIN site in northeastern Italy, which is equipped with a 100 m deep instrumented borehole. A seismic noise campaign was implemented by installing a temporary independent local surface array of seismological stations. The gathered data were used to initially estimate the shear-wave velocity (VS) profile and frequency-dependent Rayleigh-wave attenuation, and subsequently determine the QS factor via a linearized inversion method. The study compares these findings with the VS and QS values derived from analyzing weak-motion events recorded by two permanent seismic sensors positioned at the top and bottom of the well. The results confirm the potential of the inversion procedure used to obtain QS from local-scale seismic noise arrays as a promising approach for conducting attenuation studies at the local level in less geologically complex sites.
{"title":"Comparison of Near-Surface Attenuation from Surface Array-Based Seismic Noise Data and Borehole Weak-Motion Recordings at the STIN Test Site in Northeastern Italy","authors":"Ilaria Dreossi, S. Parolai","doi":"10.1785/0320230055","DOIUrl":"https://doi.org/10.1785/0320230055","url":null,"abstract":"\u0000 Seismic wave attenuation and the related shear-wave quality factor (QS) in the near surface are crucial parameters for ground motion simulations and seismic hazard assessments. Although recent approaches developed to calculate QS from seismic noise acquired by surface arrays have been accepted for practice, additional testing and comparison of results estimated using various geophysical methods are still necessary to verify the reliability of such techniques. This work presents the results of an experiment conducted at the STIN site in northeastern Italy, which is equipped with a 100 m deep instrumented borehole. A seismic noise campaign was implemented by installing a temporary independent local surface array of seismological stations. The gathered data were used to initially estimate the shear-wave velocity (VS) profile and frequency-dependent Rayleigh-wave attenuation, and subsequently determine the QS factor via a linearized inversion method. The study compares these findings with the VS and QS values derived from analyzing weak-motion events recorded by two permanent seismic sensors positioned at the top and bottom of the well. The results confirm the potential of the inversion procedure used to obtain QS from local-scale seismic noise arrays as a promising approach for conducting attenuation studies at the local level in less geologically complex sites.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":"75 27","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140794690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sylvia R. Nicovich, M. Hemphill-Haley, Thomas Leroy
The transition between the San Andreas fault (SAF) system and the southern Cascadia subduction zone (CSZ) at the Mendocino Triple Junction (MTJ) encompasses a broad zone of complex deformation, the Mendocino deformation zone. Here, there are discrepancies between types of geological structures (transform or thrust faults) and recorded geodetic velocity vectors of plate motion. Though SAF-type stress is recorded north of the MTJ, there has been little geological evidence for resultant strain at these latitudes on the coast. We focus on the Van Duzen fault (VDF)—a possible subsidiary fault of the Little Salmon fault system, one of the southernmost active thrust faults within the onshore fold and thrust belt associated with CSZ. The VDF deforms young river terraces of varying age, which we use to develop a relative-age framework to contextualize activity along the VDF. Geomorphic analysis and a paleoseismic excavation across the VDF display deformation attributed to compressional stresses, which postdates young (3–11 ka) terrace deposition, at roughly 0.06–0.38 mm/yr. We hypothesize that the transition between CSZ and SAF tectonic regimes is geologically manifest through the orientation of compressional structures (i.e., VDF), which may illuminate dynamics associated with the migrating triple junction, past and present.
圣安德烈亚斯断层（SAF）系统与卡斯卡迪亚俯冲带（CSZ）南部在门多西诺三重交界处（MTJ）的过渡地带包含一个宽广的复杂变形区，即门多西诺变形区。这里的地质结构类型（转换断层或推力断层）与记录的板块运动大地速度矢量之间存在差异。虽然在 MTJ 以北记录到了 SAF 类型的应力，但在海岸的这些纬度上，几乎没有地质证据表明会产生应变。我们将重点放在范杜增断层（VDF）上--它可能是小鲑鱼断层系统的附属断层，是与 CSZ 相关的陆上褶皱和推力带中最南端的活动推力断层之一。VDF 使不同年龄的年轻河流阶地发生变形，我们利用这些阶地建立了一个相对年龄框架，以确定 VDF 沿线的活动背景。地貌分析和横跨 VDF 的古地震挖掘显示，变形归因于压缩应力，其时间晚于年轻（3-11 ka）的阶地沉积，大约为 0.06-0.38 毫米/年。我们假设，CSZ 和 SAF 构造体系之间的过渡在地质学上是通过压缩性结构（即 VDF）的走向来体现的，这可能会揭示过去和现在与迁移的三重交界处有关的动态。
{"title":"Deformed Latest Pleistocene Fluvial Terraces Reveal Complex Active Faulting within Tectonic Transition Zone, Mendocino Triple Junction, Northern California","authors":"Sylvia R. Nicovich, M. Hemphill-Haley, Thomas Leroy","doi":"10.1785/0320230043","DOIUrl":"https://doi.org/10.1785/0320230043","url":null,"abstract":"\u0000 The transition between the San Andreas fault (SAF) system and the southern Cascadia subduction zone (CSZ) at the Mendocino Triple Junction (MTJ) encompasses a broad zone of complex deformation, the Mendocino deformation zone. Here, there are discrepancies between types of geological structures (transform or thrust faults) and recorded geodetic velocity vectors of plate motion. Though SAF-type stress is recorded north of the MTJ, there has been little geological evidence for resultant strain at these latitudes on the coast. We focus on the Van Duzen fault (VDF)—a possible subsidiary fault of the Little Salmon fault system, one of the southernmost active thrust faults within the onshore fold and thrust belt associated with CSZ. The VDF deforms young river terraces of varying age, which we use to develop a relative-age framework to contextualize activity along the VDF. Geomorphic analysis and a paleoseismic excavation across the VDF display deformation attributed to compressional stresses, which postdates young (3–11 ka) terrace deposition, at roughly 0.06–0.38 mm/yr. We hypothesize that the transition between CSZ and SAF tectonic regimes is geologically manifest through the orientation of compressional structures (i.e., VDF), which may illuminate dynamics associated with the migrating triple junction, past and present.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":"56 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140517654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Rif–Betics–Alboran region has been vital in the tectonic evolution of the western Mediterranean. Seismic images support the idea of continuous slab rollback being a prominent force in this region. However, the detailed slab structure and the physical mechanisms generating local deep (> 600 km) earthquakes remain unclear. Here, we analyze waveforms recorded from dense seismic networks above the deep earthquake beneath Granada in 2010 to study the slab structure. We discover a thin low-velocity layer (LVL) at the base of the slab to explain both the long codas observed in Morocco and the secondary arrivals observed in Spain. This LVL indicates the presence of hydrous magnesium silicates extending to ∼600 km depth, which suggests that dehydration embrittlement promotes the occurrence of deep-focus earthquakes. Our findings contradict the traditional slab model with the LVL sitting on the top of the slab, suggesting that the Alboran slab has been overturned.
{"title":"Revealing the Secrets of the Western Mediterranean: A Deep Earthquake and the Overturned Slab","authors":"Daoyuan Sun, Meghan S. Miller","doi":"10.1785/0320230049","DOIUrl":"https://doi.org/10.1785/0320230049","url":null,"abstract":"\u0000 The Rif–Betics–Alboran region has been vital in the tectonic evolution of the western Mediterranean. Seismic images support the idea of continuous slab rollback being a prominent force in this region. However, the detailed slab structure and the physical mechanisms generating local deep (> 600 km) earthquakes remain unclear. Here, we analyze waveforms recorded from dense seismic networks above the deep earthquake beneath Granada in 2010 to study the slab structure. We discover a thin low-velocity layer (LVL) at the base of the slab to explain both the long codas observed in Morocco and the secondary arrivals observed in Spain. This LVL indicates the presence of hydrous magnesium silicates extending to ∼600 km depth, which suggests that dehydration embrittlement promotes the occurrence of deep-focus earthquakes. Our findings contradict the traditional slab model with the LVL sitting on the top of the slab, suggesting that the Alboran slab has been overturned.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140519230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Improving the interpretability of phase-picking neural networks remains an important task to facilitate their deployment to routine, real-time seismic monitoring. The popular phase-picking neural networks published in the literature lack interpretability because their output prediction scores do not necessarily correspond with the reliability of phase picks and can even be highly inconsistent depending on how we window the waveform data. Here, we show that systematically shifting the waveforms during training and using an antialiasing filter within the neural network architecture can substantially improve the consistency of the output prediction scores and can even make them scale with the signal-to-noise ratios of the waveforms. We demonstrate the improvements by applying these approaches to a commonly used phase-picking neural network architecture and using waveform data from the 2019 Ridgecrest earthquake sequence.
{"title":"Making Phase-Picking Neural Networks More Consistent and Interpretable","authors":"Yongsoo Park, Brent Delbridge, David R. Shelly","doi":"10.1785/0320230054","DOIUrl":"https://doi.org/10.1785/0320230054","url":null,"abstract":"\u0000 Improving the interpretability of phase-picking neural networks remains an important task to facilitate their deployment to routine, real-time seismic monitoring. The popular phase-picking neural networks published in the literature lack interpretability because their output prediction scores do not necessarily correspond with the reliability of phase picks and can even be highly inconsistent depending on how we window the waveform data. Here, we show that systematically shifting the waveforms during training and using an antialiasing filter within the neural network architecture can substantially improve the consistency of the output prediction scores and can even make them scale with the signal-to-noise ratios of the waveforms. We demonstrate the improvements by applying these approaches to a commonly used phase-picking neural network architecture and using waveform data from the 2019 Ridgecrest earthquake sequence.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":"2013 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140516172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two earthquake sequences occurred a year apart at the Mendocino Triple Junction in northern California: first the 20 December 2021 Mw 6.1 and 6.0 Petrolia sequence, then the 20 December 2022 Mw 6.4 Ferndale sequence. To delineate active faults and understand the relationship between these sequences, we applied an automated deep-learning workflow to create enhanced and relocated earthquake catalogs for both the sequences. The enhanced catalog newly identified more than 14,000 M 0–2 earthquakes and also found 852 of 860 already cataloged events. We found that deep-learning and template-matching approaches complement each other to improve catalog completeness because deep learning finds more M 0–2 background seismicity, whereas template-matching finds the smallest M < 0 events near already known events. The enhanced catalog revealed that the 2021 Petrolia and 2022 Ferndale sequences were distinct in space and time, but adjacent in space. Though both the sequences happened in the downgoing Gorda slab, the shallower Ferndale sequence ruptured within the uppermost slab near the subduction interface, while the onshore Petrolia sequence occurred deeper in the mantle. Deep-learning-enhanced earthquake catalogs could help monitor evolving earthquake sequences, identify detailed seismogenic fault structures, and understand space–time variations in earthquake rupture and sequence behavior in a complex tectonic setting.
{"title":"Distinct Yet Adjacent Earthquake Sequences near the Mendocino Triple Junction: 20 December 2021 Mw 6.1 and 6.0 Petrolia, and 20 December 2022 Mw 6.4 Ferndale","authors":"Clara E. Yoon, David R. Shelly","doi":"10.1785/0320230053","DOIUrl":"https://doi.org/10.1785/0320230053","url":null,"abstract":"\u0000 Two earthquake sequences occurred a year apart at the Mendocino Triple Junction in northern California: first the 20 December 2021 Mw 6.1 and 6.0 Petrolia sequence, then the 20 December 2022 Mw 6.4 Ferndale sequence. To delineate active faults and understand the relationship between these sequences, we applied an automated deep-learning workflow to create enhanced and relocated earthquake catalogs for both the sequences. The enhanced catalog newly identified more than 14,000 M 0–2 earthquakes and also found 852 of 860 already cataloged events. We found that deep-learning and template-matching approaches complement each other to improve catalog completeness because deep learning finds more M 0–2 background seismicity, whereas template-matching finds the smallest M < 0 events near already known events. The enhanced catalog revealed that the 2021 Petrolia and 2022 Ferndale sequences were distinct in space and time, but adjacent in space. Though both the sequences happened in the downgoing Gorda slab, the shallower Ferndale sequence ruptured within the uppermost slab near the subduction interface, while the onshore Petrolia sequence occurred deeper in the mantle. Deep-learning-enhanced earthquake catalogs could help monitor evolving earthquake sequences, identify detailed seismogenic fault structures, and understand space–time variations in earthquake rupture and sequence behavior in a complex tectonic setting.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":"36 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140517972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. DuRoss, Z. Lifton, A. Hatem, Richard W. Briggs, Jessica A. Thompson Jobe, N. Reitman, G. Thackray, M. Zellman, Camille Collett, Harrison J. Gray, Shannon M. Mahan
The 2020 moment magnitude (Mw) 6.5 Stanley, Idaho, earthquake raised questions about the history and extent of complex faulting in the northwestern Centennial Tectonic Belt (CTB) and its relation to the Sawtooth normal fault and Eocene Trans-Challis fault system (TCFS). To explore faulting in this area, we excavated a paleoseismic trench across the Sawtooth fault along the western margin of the CTB, and compared an early Holocene (9.1 ± 2.1 ka, 1σ) rupture at the site with lacustrine paleoseismic data and fault mapping in the 2020 epicentral region. We find: (1) a history of partial to full rupture of the Sawtooth fault (Mw 6.8–7.4), (2) that shorter ruptures (Mw≤6.9) are likely along distributed and discontinuous faults in the epicentral region, (3) that this complex system that hosted the 2020 earthquake is not directly linked to the Sawtooth fault, (4) that the northeast-trending TCFS likely plays a role in controlling fault length and rupture continuity for adjacent faults, and (5) that parts of the TCFS may facilitate displacement transfer between normal faults that accommodate crustal extension and rotation. Our results help unravel complex faulting in the CTB and imply that relict structures can help inform regional seismic hazard assessments.
{"title":"Paleoseismology of the Sawtooth Fault and Implications for Fault Behavior in the Epicentral Region of the 2020 Mw 6.5 Stanley, Idaho, Earthquake","authors":"C. DuRoss, Z. Lifton, A. Hatem, Richard W. Briggs, Jessica A. Thompson Jobe, N. Reitman, G. Thackray, M. Zellman, Camille Collett, Harrison J. Gray, Shannon M. Mahan","doi":"10.1785/0320230045","DOIUrl":"https://doi.org/10.1785/0320230045","url":null,"abstract":"\u0000 The 2020 moment magnitude (Mw) 6.5 Stanley, Idaho, earthquake raised questions about the history and extent of complex faulting in the northwestern Centennial Tectonic Belt (CTB) and its relation to the Sawtooth normal fault and Eocene Trans-Challis fault system (TCFS). To explore faulting in this area, we excavated a paleoseismic trench across the Sawtooth fault along the western margin of the CTB, and compared an early Holocene (9.1 ± 2.1 ka, 1σ) rupture at the site with lacustrine paleoseismic data and fault mapping in the 2020 epicentral region. We find: (1) a history of partial to full rupture of the Sawtooth fault (Mw 6.8–7.4), (2) that shorter ruptures (Mw≤6.9) are likely along distributed and discontinuous faults in the epicentral region, (3) that this complex system that hosted the 2020 earthquake is not directly linked to the Sawtooth fault, (4) that the northeast-trending TCFS likely plays a role in controlling fault length and rupture continuity for adjacent faults, and (5) that parts of the TCFS may facilitate displacement transfer between normal faults that accommodate crustal extension and rotation. Our results help unravel complex faulting in the CTB and imply that relict structures can help inform regional seismic hazard assessments.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":"39 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140525491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the recent years, coda-wave interferometry from seismic noise correlation functions has been increasingly used for volcanic eruption forecasting through velocity changes observed in the crust. Because La Palma Island in the Canary Archipelago is very well instrumented, we studied the possible velocity variations related to the last Cumbre Vieja eruption on 19 September 2021, aiming to obtain clear variations in the seismic velocity. For this purpose, we used the moving-window cross-spectral analysis technique for seismic noise within the 0.1–1.0 Hz frequency interval for determining two- and single-station cross-component correlations. During the 2018–2022 observation period, we first detected a seasonal seismic velocity variation possibly caused by annual rainfall and the induced pore pressure change. On 12 September 2021, a dramatic decrease in the velocity of −0.15% was detected, leading to the volcanic eruption at Cumbre Vieja seven days later. The results are compatible with those of models proposed for rapid magma migration from a shallow reservoir at 11 km to the surface.
{"title":"Seismic Velocity Variations Observed Prior to the La Palma Volcano Eruption on 19 September 2021, in Cumbre Vieja, Canary Islands (Spain)","authors":"J. Mezcua, J. Rueda","doi":"10.1785/0320230048","DOIUrl":"https://doi.org/10.1785/0320230048","url":null,"abstract":"\u0000 In the recent years, coda-wave interferometry from seismic noise correlation functions has been increasingly used for volcanic eruption forecasting through velocity changes observed in the crust. Because La Palma Island in the Canary Archipelago is very well instrumented, we studied the possible velocity variations related to the last Cumbre Vieja eruption on 19 September 2021, aiming to obtain clear variations in the seismic velocity. For this purpose, we used the moving-window cross-spectral analysis technique for seismic noise within the 0.1–1.0 Hz frequency interval for determining two- and single-station cross-component correlations. During the 2018–2022 observation period, we first detected a seasonal seismic velocity variation possibly caused by annual rainfall and the induced pore pressure change. On 12 September 2021, a dramatic decrease in the velocity of −0.15% was detected, leading to the volcanic eruption at Cumbre Vieja seven days later. The results are compatible with those of models proposed for rapid magma migration from a shallow reservoir at 11 km to the surface.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":" 33","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139393427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As glaciers retreat, landslide-driven tsunamis pose mounting threats across the high latitudes. The recent landslide tsunamis in Alaska and Greenland have spurred efforts to forecast and monitor these events. We use nine large landslides spanning southern Alaska to test an approach for rapid detection and characterization. We use long-period seismograms recorded within three minutes of the start of a landslide to estimate the location and approximate volume. In the presence of good seismic network coverage, location errors are no more than a few kilometers, and detection limits are well below 1 Mm3. The combination of detection time, location, and size provides the ability to rapidly determine whether a landslide occurred close to open water and, if so, its tsunamigenic potential. Our approach is rapid enough to support National Oceanic and Atmospheric Administration (NOAA)’s five-minute tsunami warning goal. The historical analysis we present provides the foundation and parameter tuning for a prototype system that is now providing real-time detections.
{"title":"Toward the Rapid Seismic Assessment of Landslides in Coastal Alaska","authors":"E. Karasözen, M. West","doi":"10.1785/0320230044","DOIUrl":"https://doi.org/10.1785/0320230044","url":null,"abstract":"\u0000 As glaciers retreat, landslide-driven tsunamis pose mounting threats across the high latitudes. The recent landslide tsunamis in Alaska and Greenland have spurred efforts to forecast and monitor these events. We use nine large landslides spanning southern Alaska to test an approach for rapid detection and characterization. We use long-period seismograms recorded within three minutes of the start of a landslide to estimate the location and approximate volume. In the presence of good seismic network coverage, location errors are no more than a few kilometers, and detection limits are well below 1 Mm3. The combination of detection time, location, and size provides the ability to rapidly determine whether a landslide occurred close to open water and, if so, its tsunamigenic potential. Our approach is rapid enough to support National Oceanic and Atmospheric Administration (NOAA)’s five-minute tsunami warning goal. The historical analysis we present provides the foundation and parameter tuning for a prototype system that is now providing real-time detections.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":"23 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140523862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ross Heyburn, David N. Green, A. Nippress, Neil D. Selby
On 26 September 2022, two seismic events were detected by regional seismic networks, coincident with media-reported leaks from the Nord Stream gas pipelines in the western Baltic Sea. In this study, we analyze seismic and infrasound signals from these two events and compare the seismic signals with those from other nearby seismic events such as underwater explosions and presumed earthquakes. Arrival times of seismic signals from the events on 26 September 2022 are used to show that the epicenters for both the events are in the vicinity of the Nord Stream pipelines. Signals from the two events display features that are characteristic of sources occurring near the seafloor. Observed P/S ratios from the Nord Stream events are also different from those observed for nearby presumed earthquakes. The observed seismic and infrasound signals are longer duration than would be expected from a single explosive source and show similarities with those observed from underwater volcano eruptions and gas pipeline explosions. The difference between seismic magnitudes estimated for the first Nord Stream pipeline event (MLP 2.32) and an event associated with the rupture of the Balticconnector pipeline on 7 October 2023 (MLP 1.09) is consistent with the estimated potential energy ratio of the gas in the pipelines. This suggests that the initial seismic signals from the first Nord Stream event may be dominated by energy generated by the venting of gas.
{"title":"The 26 September 2022 Nord Stream Events: Insights from Nearby Seismic Events","authors":"Ross Heyburn, David N. Green, A. Nippress, Neil D. Selby","doi":"10.1785/0320230047","DOIUrl":"https://doi.org/10.1785/0320230047","url":null,"abstract":"\u0000 On 26 September 2022, two seismic events were detected by regional seismic networks, coincident with media-reported leaks from the Nord Stream gas pipelines in the western Baltic Sea. In this study, we analyze seismic and infrasound signals from these two events and compare the seismic signals with those from other nearby seismic events such as underwater explosions and presumed earthquakes. Arrival times of seismic signals from the events on 26 September 2022 are used to show that the epicenters for both the events are in the vicinity of the Nord Stream pipelines. Signals from the two events display features that are characteristic of sources occurring near the seafloor. Observed P/S ratios from the Nord Stream events are also different from those observed for nearby presumed earthquakes. The observed seismic and infrasound signals are longer duration than would be expected from a single explosive source and show similarities with those observed from underwater volcano eruptions and gas pipeline explosions. The difference between seismic magnitudes estimated for the first Nord Stream pipeline event (MLP 2.32) and an event associated with the rupture of the Balticconnector pipeline on 7 October 2023 (MLP 1.09) is consistent with the estimated potential energy ratio of the gas in the pipelines. This suggests that the initial seismic signals from the first Nord Stream event may be dominated by energy generated by the venting of gas.","PeriodicalId":273018,"journal":{"name":"The Seismic Record","volume":"87 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139454521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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