Pub Date : 2024-09-18DOI: 10.1186/s40562-024-00347-5
Zi-ying Xuan, Fei Zheng, Jiang Zhu
Implementing the strongly coupled data assimilation (SCDA) in coupled earth system models remains big challenging, primarily due to accurately estimating the coupled cross background-error covariance. In this work, through simplified two-variable one-dimensional assimilation experiments focusing on the air–sea interactions over the tropical pacific, we aim to clarify that SCDA based on the variance–covariance correlation, such as the ensemble-based SCDA, is limited in handling the inherent nonlinear relations between cross-sphere variables and provides a background matrix containing linear information only. These limitations also lead to the analysis distributions deviating from the truth and miscalculating the strength of rare extreme events. However, free from linear or Gaussian assumptions, the application of the data-driven machine learning (ML) method, such as multilayer perceptron, on SCDA circumvents the expensive matrix operations by avoiding the explicit calculation of background matrix. This strategy presents comprehensively superior performance than the conventional ensemble-based assimilation strategy, particularly in representing the strongly nonlinear relationships between cross-sphere variables and reproducing long-tailed distributions, which help capture the occurrence of small probability events. It is also demonstrated to be cost-effective and has great potential to generate a more accurate initial condition for coupled models, especially in facilitating prediction tasks of the extreme events.
{"title":"The effectiveness of machine learning methods in the nonlinear coupled data assimilation","authors":"Zi-ying Xuan, Fei Zheng, Jiang Zhu","doi":"10.1186/s40562-024-00347-5","DOIUrl":"https://doi.org/10.1186/s40562-024-00347-5","url":null,"abstract":"Implementing the strongly coupled data assimilation (SCDA) in coupled earth system models remains big challenging, primarily due to accurately estimating the coupled cross background-error covariance. In this work, through simplified two-variable one-dimensional assimilation experiments focusing on the air–sea interactions over the tropical pacific, we aim to clarify that SCDA based on the variance–covariance correlation, such as the ensemble-based SCDA, is limited in handling the inherent nonlinear relations between cross-sphere variables and provides a background matrix containing linear information only. These limitations also lead to the analysis distributions deviating from the truth and miscalculating the strength of rare extreme events. However, free from linear or Gaussian assumptions, the application of the data-driven machine learning (ML) method, such as multilayer perceptron, on SCDA circumvents the expensive matrix operations by avoiding the explicit calculation of background matrix. This strategy presents comprehensively superior performance than the conventional ensemble-based assimilation strategy, particularly in representing the strongly nonlinear relationships between cross-sphere variables and reproducing long-tailed distributions, which help capture the occurrence of small probability events. It is also demonstrated to be cost-effective and has great potential to generate a more accurate initial condition for coupled models, especially in facilitating prediction tasks of the extreme events.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"17 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257531","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}
Pub Date : 2024-09-13DOI: 10.1186/s40562-024-00358-2
Su-Chin Chang, Mei-Fei Chu, Jui-Pin Wang, Yu-Ming Lai, Sheng-Rong Song, Sidney R. Hemming, Samuel Wai-Pan Ng, Timothy Dylan Chow
The Tatun Volcano Group (TVG) is located at the northern end of Taiwan, ~ 15 km from the center of Taipei, a metropolitan area of over seven million inhabitants. A volcanic eruption by the TVG of any type or scale could cause catastrophic human and economic impacts. This paper summarizes previous geochemical, geophysical, and geochronological reports and highlights why the widely accepted age model does not comport with the latest observations. This study also reports novel 40Ar/39Ar ages for two andesite samples and one basalt sample from the TVG. A sample collected from Chihsingshan yields a robust 40Ar/39Ar age of 0.081 ± 0.005 Ma. This provides the first direct evidence of TVG volcanic activity after 0.1 Ma. Two samples yield 0.28 ± 0.02 Ma for Tatunshan and 0.159 ± 0.017 Ma for Honglushan. The younger ages refute previously proposed age models for the TVG. Along with new drone photos and LiDAR images, the age data help resolve eruptive history and advance understanding of volcanic hazards and hazard mitigation in Taiwan and surrounding areas.
{"title":"Volcanic activity around Taipei, Taiwan: new data and perspectives on the Tatun Volcano Group","authors":"Su-Chin Chang, Mei-Fei Chu, Jui-Pin Wang, Yu-Ming Lai, Sheng-Rong Song, Sidney R. Hemming, Samuel Wai-Pan Ng, Timothy Dylan Chow","doi":"10.1186/s40562-024-00358-2","DOIUrl":"https://doi.org/10.1186/s40562-024-00358-2","url":null,"abstract":"The Tatun Volcano Group (TVG) is located at the northern end of Taiwan, ~ 15 km from the center of Taipei, a metropolitan area of over seven million inhabitants. A volcanic eruption by the TVG of any type or scale could cause catastrophic human and economic impacts. This paper summarizes previous geochemical, geophysical, and geochronological reports and highlights why the widely accepted age model does not comport with the latest observations. This study also reports novel 40Ar/39Ar ages for two andesite samples and one basalt sample from the TVG. A sample collected from Chihsingshan yields a robust 40Ar/39Ar age of 0.081 ± 0.005 Ma. This provides the first direct evidence of TVG volcanic activity after 0.1 Ma. Two samples yield 0.28 ± 0.02 Ma for Tatunshan and 0.159 ± 0.017 Ma for Honglushan. The younger ages refute previously proposed age models for the TVG. Along with new drone photos and LiDAR images, the age data help resolve eruptive history and advance understanding of volcanic hazards and hazard mitigation in Taiwan and surrounding areas.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"14 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194317","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}
Pub Date : 2024-09-09DOI: 10.1186/s40562-024-00357-3
Masataka Sakai, Masako Hori, Ryu Uemura, Bassam Ghaleb, Daniele L. Pinti, Mahiro Yumiba, Masafumi Murayama, Akihiro Kano
Stalagmites are useful archives in reconstructing paleoclimates: most paleoclimate studies used stalagmites that are distributed in specific locations and ages. We examined a stalagmite (GYM-1) collected from Nara Prefecture, central Japan, where limestone areas are limited. Applying 238U–234U method, the ages of GYM-1 were determined as 744 ± 70 to 677 ± 74 ka (based only on analytical uncertainties, 1σ). Even assuming a 10% uncertainty in the initial activity of 234U/238U, (234U/238U)0, this age could be still older than 460 ka. Temperatures calculated based on δD in the fluid inclusions and δ18O in the calcium carbonate ranged from 9.0 to 11.9 °C (10.8 ± 0.9 °C on average) or from 6.0 to 9.1 °C (7.9 ± 0.9 °C on average) depending on the equation. The estimated temperature suggests that GYM-1 formed during an interglacial period of the Middle Pleistocene. Synchronous behavior of isotopic values with lamination likely reflects seasonal temperature in a highly ventilated cave system.
{"title":"A snapshot of the climate in the Middle Pleistocene inferred from a stalagmite from central Japan","authors":"Masataka Sakai, Masako Hori, Ryu Uemura, Bassam Ghaleb, Daniele L. Pinti, Mahiro Yumiba, Masafumi Murayama, Akihiro Kano","doi":"10.1186/s40562-024-00357-3","DOIUrl":"https://doi.org/10.1186/s40562-024-00357-3","url":null,"abstract":"Stalagmites are useful archives in reconstructing paleoclimates: most paleoclimate studies used stalagmites that are distributed in specific locations and ages. We examined a stalagmite (GYM-1) collected from Nara Prefecture, central Japan, where limestone areas are limited. Applying 238U–234U method, the ages of GYM-1 were determined as 744 ± 70 to 677 ± 74 ka (based only on analytical uncertainties, 1σ). Even assuming a 10% uncertainty in the initial activity of 234U/238U, (234U/238U)0, this age could be still older than 460 ka. Temperatures calculated based on δD in the fluid inclusions and δ18O in the calcium carbonate ranged from 9.0 to 11.9 °C (10.8 ± 0.9 °C on average) or from 6.0 to 9.1 °C (7.9 ± 0.9 °C on average) depending on the equation. The estimated temperature suggests that GYM-1 formed during an interglacial period of the Middle Pleistocene. Synchronous behavior of isotopic values with lamination likely reflects seasonal temperature in a highly ventilated cave system.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"11 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194318","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}
Pub Date : 2024-08-27DOI: 10.1186/s40562-024-00355-5
Zaiji Gao, Ya Sun, Jiwen Huang, Qiu Li
We construct the 3D Shear wave velocity and azimuthal anisotropy images in the southern Chuandian block using phase velocity dispersion of Rayleigh wave in the period of 5–45 s. The images show two extensive low-velocity zones with a depth range of 20–40 km. The west range of the low-velocity extends from the Lijiang-Xiaojinhe fault to the Red River fault, while its east range follows along the Xiaojiang fault. Two ranges of low velocities are merged at the southern inner belt of the Emeishan Large Igneous Provinces (ELIP). The observed fast directions of azimuthal anisotropy are consistent with the extension of low-velocity ranges at the lower crust. The findings reveal the presence of two potential weak channels in the lower crust, characterized by low-velocity zones, which align with the hypothesis of lower crustal flow. Meanwhile, the crust around the inner belt of ELIP exhibits a high-velocity body characterized by a northeast-trending and counter-clockwise azimuthal anisotropy. Combined with geological data, we attribute the high S-velocity to a mafic–ultramafic magma reservoir of the ELIP, which blocks the continuity of crustal flow within the southern Chuandian block, thus dividing the lower crustal flow into two branches. Additionally, we also find the fast directions of azimuthal anisotropy above 20 km align well with the strike-slip fault orientations. The above research results indicate that the crustal deformation in the southern Chuandian block is likely attributed to the joint action of the two deformation mechanisms. One involves a lower crustal flow model, while the other entails rigid extrusion controlled by the deep-seated, large-scale strike-slip faults in the upper crust.
{"title":"The crustal deformation mechanism of southern Chuandian block: constrained by S wave velocity and its azimuthal anisotropy","authors":"Zaiji Gao, Ya Sun, Jiwen Huang, Qiu Li","doi":"10.1186/s40562-024-00355-5","DOIUrl":"https://doi.org/10.1186/s40562-024-00355-5","url":null,"abstract":"We construct the 3D Shear wave velocity and azimuthal anisotropy images in the southern Chuandian block using phase velocity dispersion of Rayleigh wave in the period of 5–45 s. The images show two extensive low-velocity zones with a depth range of 20–40 km. The west range of the low-velocity extends from the Lijiang-Xiaojinhe fault to the Red River fault, while its east range follows along the Xiaojiang fault. Two ranges of low velocities are merged at the southern inner belt of the Emeishan Large Igneous Provinces (ELIP). The observed fast directions of azimuthal anisotropy are consistent with the extension of low-velocity ranges at the lower crust. The findings reveal the presence of two potential weak channels in the lower crust, characterized by low-velocity zones, which align with the hypothesis of lower crustal flow. Meanwhile, the crust around the inner belt of ELIP exhibits a high-velocity body characterized by a northeast-trending and counter-clockwise azimuthal anisotropy. Combined with geological data, we attribute the high S-velocity to a mafic–ultramafic magma reservoir of the ELIP, which blocks the continuity of crustal flow within the southern Chuandian block, thus dividing the lower crustal flow into two branches. Additionally, we also find the fast directions of azimuthal anisotropy above 20 km align well with the strike-slip fault orientations. The above research results indicate that the crustal deformation in the southern Chuandian block is likely attributed to the joint action of the two deformation mechanisms. One involves a lower crustal flow model, while the other entails rigid extrusion controlled by the deep-seated, large-scale strike-slip faults in the upper crust.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"38 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194352","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}
Pub Date : 2024-08-22DOI: 10.1186/s40562-024-00352-8
Lejiang Yu, Shiyuan Zhong, Cuijuan Sui, Bo Sun
Previous research has explored the impact of the Interdecadal Pacific Oscillation (IPO) and Atlantic Multidecadal Oscillation (AMO) on Antarctic surface air temperature (SAT) variability. However, a notable gap remains in our comprehension concerning the response of Antarctic SAT to the four phase combinations of IPO and AMO. In this study, we unveil unique patterns of Antarctic SAT anomalies during four distinct sub-periods based on the phases of IPO and AMO. Notably, Antarctic SAT anomalies exhibit a considerable seasonality, with the most pronounced (weakest) anomalies occurring during the austral winter (summer), a phenomenon consistent across all four sub-periods. These different anomalous SST patterns trigger varying convective rainfall patterns, consequently initiating distinct wavetrains that propagate into the Southern Ocean. These different wavetrains, in turn, induce variations in sea level pressure and surface wind fields, resulting in different Antarctic SAT anomalies primarily through mechanisms related to horizontal thermal advection and downward longwave radiation. Understanding the variability in Antarctic surface air temperature (SAT) is crucial for unraveling the complex dynamics of the polar climate system and its broader implications for global climate patterns. Fewer studies highlighted the impacts of the four combinations of the phases of IPO and AMO on Antarctic SAT anomalies. In this study, we uncover distinct patterns of Antarctic SAT anomalies during four different periods based on the phases of IPO and AMO. We note that Antarctic SAT anomalies exhibit a considerable seasonality, with the most pronounced (weakest) anomalies occurring during the austral winter (summer), consistently across all four periods. The anomalous SST patterns during different periods trigger distinct wavetrains that propagate into the Southern Ocean, inducing variations in sea level pressure, surface wind fields, and Antarctic SAT anomalies. These findings bear substantial implications for the prediction of Antarctic seasonal SAT variations on interdecadal timescales.
以往的研究探讨了年代际太平洋涛动（IPO）和大西洋多年涛动（AMO）对南极表面气温（SAT）变化的影响。然而，我们在理解南极 SAT 对 IPO 和 AMO 的四个阶段组合的响应方面仍存在明显差距。在本研究中，我们根据 IPO 和 AMO 的不同阶段，揭示了南极 SAT 异常在四个不同子时期的独特模式。值得注意的是，南极 SAT 异常表现出相当强的季节性，最明显（最微弱）的异常出现在澳大利亚的冬季（夏季），这一现象在所有四个子时期都是一致的。这些不同的海温异常模式触发了不同的对流降雨模式，从而引发了传播到南大洋的不同波系。这些不同的波系反过来又引起海平面气压和海面风场的变化，主要通过与水平热平流和向下长波辐射有关的机制导致不同的南极 SAT 异常。了解南极表面气温（SAT）的变化对于揭示极地气候系统的复杂动态及其对全球气候模式的广泛影响至关重要。较少研究强调 IPO 和 AMO 的四个阶段组合对南极 SAT 异常的影响。在本研究中，我们根据 IPO 和 AMO 的不同阶段，发现了南极 SAT 异常在四个不同时期的不同模式。我们注意到，南极 SAT 异常表现出相当强的季节性，最明显（最微弱）的异常出现在澳大利亚的冬季（夏季），这在所有四个时期都是一致的。不同时期的海温异常模式会引发不同的波系，传播到南大洋，引起海平面气压、表面风场和南极 SAT 异常的变化。这些发现对预测南极季节性 SAT 在年代际尺度上的变化具有重大意义。
{"title":"Surface air temperature anomalies over Antarctica and the Southern ocean induced by interactions between the interdecadal Pacific oscillation and Atlantic multidecadal oscillation","authors":"Lejiang Yu, Shiyuan Zhong, Cuijuan Sui, Bo Sun","doi":"10.1186/s40562-024-00352-8","DOIUrl":"https://doi.org/10.1186/s40562-024-00352-8","url":null,"abstract":"Previous research has explored the impact of the Interdecadal Pacific Oscillation (IPO) and Atlantic Multidecadal Oscillation (AMO) on Antarctic surface air temperature (SAT) variability. However, a notable gap remains in our comprehension concerning the response of Antarctic SAT to the four phase combinations of IPO and AMO. In this study, we unveil unique patterns of Antarctic SAT anomalies during four distinct sub-periods based on the phases of IPO and AMO. Notably, Antarctic SAT anomalies exhibit a considerable seasonality, with the most pronounced (weakest) anomalies occurring during the austral winter (summer), a phenomenon consistent across all four sub-periods. These different anomalous SST patterns trigger varying convective rainfall patterns, consequently initiating distinct wavetrains that propagate into the Southern Ocean. These different wavetrains, in turn, induce variations in sea level pressure and surface wind fields, resulting in different Antarctic SAT anomalies primarily through mechanisms related to horizontal thermal advection and downward longwave radiation. Understanding the variability in Antarctic surface air temperature (SAT) is crucial for unraveling the complex dynamics of the polar climate system and its broader implications for global climate patterns. Fewer studies highlighted the impacts of the four combinations of the phases of IPO and AMO on Antarctic SAT anomalies. In this study, we uncover distinct patterns of Antarctic SAT anomalies during four different periods based on the phases of IPO and AMO. We note that Antarctic SAT anomalies exhibit a considerable seasonality, with the most pronounced (weakest) anomalies occurring during the austral winter (summer), consistently across all four periods. The anomalous SST patterns during different periods trigger distinct wavetrains that propagate into the Southern Ocean, inducing variations in sea level pressure, surface wind fields, and Antarctic SAT anomalies. These findings bear substantial implications for the prediction of Antarctic seasonal SAT variations on interdecadal timescales. ","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"41 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194319","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}
Pub Date : 2024-08-22DOI: 10.1186/s40562-024-00356-4
Xiaoqi Xu, Jiping Liu, Gang Huang, Yifan Ding
In this study, we investigate the climatology and trend of explosive cyclones (ECs) over the Southern Ocean (50oS–70oS) during 1980–2020 by combining a method that is most suited for identifying and tracking cyclones in the Southern Ocean and a latest climate reanalysis. On average, approximately 50 ECs are generated annually over the Southern Ocean, with a significant increasing trend of 2.3 per decade during the studying period. This increasing trend is dominated by the trend of strong ECs, particularly in autumn. We analyze the dynamical and thermodynamical effects associated with multiple deepened strong ECs in autumn over an identified key region in the southern Pacific Ocean sector (155oW–170oW, 50oS–65oS), where the density of the initiation of ECs shows the largest increasing trend in autumn. The composite analysis reveals the general patterns and duration of the effects on the atmosphere, ocean, and sea ice associated with multiple ECs in the southern Pacific Ocean. The results indicate that the deepened strong ECs are associated with significant changes in meridional winds, downward longwave radiation, and sensible and latent heat fluxes. These changes lead to cold sea surface temperature anomalies in the northeast of the key region, reaching a maximum 5–7 days after the EC deepening, and the increased sea ice cover south of the key region, peaking 4–5 days after the EC deepening.
{"title":"Distribution and trend of explosive cyclones over the Southern Ocean and associated atmospheric and oceanic changes during 1980–2020","authors":"Xiaoqi Xu, Jiping Liu, Gang Huang, Yifan Ding","doi":"10.1186/s40562-024-00356-4","DOIUrl":"https://doi.org/10.1186/s40562-024-00356-4","url":null,"abstract":"In this study, we investigate the climatology and trend of explosive cyclones (ECs) over the Southern Ocean (50oS–70oS) during 1980–2020 by combining a method that is most suited for identifying and tracking cyclones in the Southern Ocean and a latest climate reanalysis. On average, approximately 50 ECs are generated annually over the Southern Ocean, with a significant increasing trend of 2.3 per decade during the studying period. This increasing trend is dominated by the trend of strong ECs, particularly in autumn. We analyze the dynamical and thermodynamical effects associated with multiple deepened strong ECs in autumn over an identified key region in the southern Pacific Ocean sector (155oW–170oW, 50oS–65oS), where the density of the initiation of ECs shows the largest increasing trend in autumn. The composite analysis reveals the general patterns and duration of the effects on the atmosphere, ocean, and sea ice associated with multiple ECs in the southern Pacific Ocean. The results indicate that the deepened strong ECs are associated with significant changes in meridional winds, downward longwave radiation, and sensible and latent heat fluxes. These changes lead to cold sea surface temperature anomalies in the northeast of the key region, reaching a maximum 5–7 days after the EC deepening, and the increased sea ice cover south of the key region, peaking 4–5 days after the EC deepening. ","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"25 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194349","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}
Accurately imaging seismogenic structures is crucial for seismic hazard assessment. This is especially important around the deformation front (DF) region off SW Taiwan, where seismic potential is high but the fault structure and seismic activity are still poorly understood. Here, we present a comprehensive delineation of seismogenic structures along the onshore and offshore DF of SW Taiwan, utilizing hypocenter relocations and first-motion focal mechanism solutions from January 1991 to March 2019. Five distinctive seismogenic structures are delineated. Particularly, the energetic seismic activity initialled after the 2017 Mw5.3 Tainan earthquake and migrated northeastward along the western side of the DF. The offshore trace of the DF could serve as a boundary delimiting the seismic activity driven by the flexural stress of the subducted Eurasia Plate to the west of the DF. This observation could constrain the magnitude estimation of future earthquakes offshore SW Taiwan. Meanwhile, the areas with higher seismic moment release are located near the DF rather than known faults, indicating that the DF may dominate the seismic moment release. However, further study is warranted into the intricate relationship among seismic strain variation, the structure of DF, and seismic activity to further understand the seismic potential. Our first-motion focal mechanism solutions show that several earthquakes in SW Taiwan were characterized by P-axis orientations parallel to the strike of the Taiwan orogeny. Those events are preferably explained by the lateral compression induced by the ongoing collision between the Eurasia and Philippine Sea plates.
{"title":"Seismogenic structures along the deformation front from onshore to offshore SW Taiwan","authors":"Wen-Nan Wu, Jing-Yi Lin, Wen-Bin Doo, Chung-Liang Lo, Shu-Kun Hsu","doi":"10.1186/s40562-024-00354-6","DOIUrl":"https://doi.org/10.1186/s40562-024-00354-6","url":null,"abstract":"Accurately imaging seismogenic structures is crucial for seismic hazard assessment. This is especially important around the deformation front (DF) region off SW Taiwan, where seismic potential is high but the fault structure and seismic activity are still poorly understood. Here, we present a comprehensive delineation of seismogenic structures along the onshore and offshore DF of SW Taiwan, utilizing hypocenter relocations and first-motion focal mechanism solutions from January 1991 to March 2019. Five distinctive seismogenic structures are delineated. Particularly, the energetic seismic activity initialled after the 2017 Mw5.3 Tainan earthquake and migrated northeastward along the western side of the DF. The offshore trace of the DF could serve as a boundary delimiting the seismic activity driven by the flexural stress of the subducted Eurasia Plate to the west of the DF. This observation could constrain the magnitude estimation of future earthquakes offshore SW Taiwan. Meanwhile, the areas with higher seismic moment release are located near the DF rather than known faults, indicating that the DF may dominate the seismic moment release. However, further study is warranted into the intricate relationship among seismic strain variation, the structure of DF, and seismic activity to further understand the seismic potential. Our first-motion focal mechanism solutions show that several earthquakes in SW Taiwan were characterized by P-axis orientations parallel to the strike of the Taiwan orogeny. Those events are preferably explained by the lateral compression induced by the ongoing collision between the Eurasia and Philippine Sea plates. ","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"5 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194350","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}
Pub Date : 2024-08-14DOI: 10.1186/s40562-024-00353-7
Andrean V. H. Simanjuntak, Kadek H. Palgunadi, Pepen Supendi, Umar Muksin, Endra Gunawan, Sri Widiyantoro, Nicholas Rawlinson, Mudrik R. Daryono, D. Daryono, Dwikorita Karnawati, Nuraini R. Hanifa, Cecep Pratama, Rachmah Ida
Two shallow earthquakes of moment magnitude 6.2 and 5.8 occurred in the central arm of Sulawesi on 26 July 2021 and 26 August 2021, respectively. The fault responsible for the earthquake had previously only been partially mapped, thus making further analysis of its characteristics crucial for the assessment of seismic hazard. In this study, we exploit data from a regional seismic network, relocate the associated seismicity using the double difference method with an updated velocity model, determine focal mechanisms from full-waveform inversion, and analyze the static stress changes caused by the mainshock. Our relocated hypocenters and focal mechanism solutions reveal two earthquake clusters, one at the Central Balantak Fault that exhibits normal slip on a SE–NW trending rupture, and the other at the West Balantak Fault, which exhibits dextral strike-slip motion on a SE–NW trending rupture. The additional static stress increase transferred by the Mw 6.2 mainshock may have triggered the subsequent Mw 5.8 event. A detailed assessment of previously unmapped faults in Central Sulawesi is essential for a more comprehensive understanding of seismic hazard in the region.
{"title":"The western extension of the Balantak Fault revealed by the 2021 earthquake cascade in the central arm of Sulawesi, Indonesia","authors":"Andrean V. H. Simanjuntak, Kadek H. Palgunadi, Pepen Supendi, Umar Muksin, Endra Gunawan, Sri Widiyantoro, Nicholas Rawlinson, Mudrik R. Daryono, D. Daryono, Dwikorita Karnawati, Nuraini R. Hanifa, Cecep Pratama, Rachmah Ida","doi":"10.1186/s40562-024-00353-7","DOIUrl":"https://doi.org/10.1186/s40562-024-00353-7","url":null,"abstract":"Two shallow earthquakes of moment magnitude 6.2 and 5.8 occurred in the central arm of Sulawesi on 26 July 2021 and 26 August 2021, respectively. The fault responsible for the earthquake had previously only been partially mapped, thus making further analysis of its characteristics crucial for the assessment of seismic hazard. In this study, we exploit data from a regional seismic network, relocate the associated seismicity using the double difference method with an updated velocity model, determine focal mechanisms from full-waveform inversion, and analyze the static stress changes caused by the mainshock. Our relocated hypocenters and focal mechanism solutions reveal two earthquake clusters, one at the Central Balantak Fault that exhibits normal slip on a SE–NW trending rupture, and the other at the West Balantak Fault, which exhibits dextral strike-slip motion on a SE–NW trending rupture. The additional static stress increase transferred by the Mw 6.2 mainshock may have triggered the subsequent Mw 5.8 event. A detailed assessment of previously unmapped faults in Central Sulawesi is essential for a more comprehensive understanding of seismic hazard in the region.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"14 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194360","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}
In this study, the precursory seismic activity before a major earthquake was investigated by using the Pattern Informatics (PI) algorithm along the Sagaing fault zone (SFZ), Central Myanmar. After improving the earthquake catalog, the completeness of seismicity data with Mw ≥ 3.6 reported during 1980–2020 was used in retrospective testing to find the suitable parameters of the PI algorithm. According to the retrospective test with 6 cases of different forecast period times related to Mw ≥ 5.0 earthquakes, including verification using the relative operating characteristics (ROC) diagram, the characteristic parameters of both time intervals (change time and forecast time window) = 10 years and target forecast earthquake magnitude Mw ≥ 5.0 are suitable parameters for PI investigation along the SFZ. Therefore, these parameters were applied with the most up-to-date seismic dataset to evaluate the prospective areas of upcoming major earthquakes. The results reveal that the Myitkyina and the vicinity of Naypyidaw might be at risk of a major earthquake in the future. Therefore, effective earthquake mitigation plans should be urgently arranged.
{"title":"Precursory seismic quiescence of major earthquakes along the Sagaing fault zone, central Myanmar: application of the pattern informatics technique","authors":"Premwadee Traitangwong, Sutthikan Khamsiri, Santi Pailoplee","doi":"10.1186/s40562-024-00351-9","DOIUrl":"https://doi.org/10.1186/s40562-024-00351-9","url":null,"abstract":"In this study, the precursory seismic activity before a major earthquake was investigated by using the Pattern Informatics (PI) algorithm along the Sagaing fault zone (SFZ), Central Myanmar. After improving the earthquake catalog, the completeness of seismicity data with Mw ≥ 3.6 reported during 1980–2020 was used in retrospective testing to find the suitable parameters of the PI algorithm. According to the retrospective test with 6 cases of different forecast period times related to Mw ≥ 5.0 earthquakes, including verification using the relative operating characteristics (ROC) diagram, the characteristic parameters of both time intervals (change time and forecast time window) = 10 years and target forecast earthquake magnitude Mw ≥ 5.0 are suitable parameters for PI investigation along the SFZ. Therefore, these parameters were applied with the most up-to-date seismic dataset to evaluate the prospective areas of upcoming major earthquakes. The results reveal that the Myitkyina and the vicinity of Naypyidaw might be at risk of a major earthquake in the future. Therefore, effective earthquake mitigation plans should be urgently arranged.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"30 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948064","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}
Streamflow in source region of Yellow River (SRYR) matters with regard to the adjacent and downstream water resources. Intraseasonal oscillation (ISO) in the streamflow in SRYR is of great significance to the sub-seasonal prediction of streamflow in SRYR, but is unknown. Here, we first report a 30–60-day ISO in the streamflow in SRYR, which is regulated by the atmospheric 30–60-day ISO at mid-high latitude over North Eurasia. The 30–60-day ISO in atmosphere is featured by a Rossby wavetrain, and the wave energy propagates southward onto the TP, which causes anomalous wind response over TP. The leading anomalous high (low) with anti-cyclonic (cyclonic) wind anomalies over the TP favors dry (wet) air in lower troposphere in SRYR, via enhancing the water vapor divergence (convergence). Dry (wet) air always results in strong (weak) evaporation from the Yellow River, which causes the later streamflow valley (peak) and thereby the 30–60-day ISO in the streamflow in SRYR.
{"title":"Origin of the 30–60-day intraseasonal oscillation of streamflow in source region of Yellow River in China: a perspective of the atmospheric signals from mid-high latitude","authors":"Lun Li, Congwen Zhu, Xiangde Xu, Ziyan Zheng, Shuangmei Ma, Wanyi Sun","doi":"10.1186/s40562-024-00348-4","DOIUrl":"https://doi.org/10.1186/s40562-024-00348-4","url":null,"abstract":"Streamflow in source region of Yellow River (SRYR) matters with regard to the adjacent and downstream water resources. Intraseasonal oscillation (ISO) in the streamflow in SRYR is of great significance to the sub-seasonal prediction of streamflow in SRYR, but is unknown. Here, we first report a 30–60-day ISO in the streamflow in SRYR, which is regulated by the atmospheric 30–60-day ISO at mid-high latitude over North Eurasia. The 30–60-day ISO in atmosphere is featured by a Rossby wavetrain, and the wave energy propagates southward onto the TP, which causes anomalous wind response over TP. The leading anomalous high (low) with anti-cyclonic (cyclonic) wind anomalies over the TP favors dry (wet) air in lower troposphere in SRYR, via enhancing the water vapor divergence (convergence). Dry (wet) air always results in strong (weak) evaporation from the Yellow River, which causes the later streamflow valley (peak) and thereby the 30–60-day ISO in the streamflow in SRYR.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"45 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141948065","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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