The purpose of this work is to carry out seismically induced landslide probabilistic hazard mapping for future seismic scenarios of Aba Prefecture and Chengdu Plain region, Sichuan Province, China. Nine earthquake events that occurred in the regions and neighboring areas are selected, which include a total of 251,260 landslide records. This work used 12 influencing factors including elevation, slope, aspect, relief, topographic wetness index (TWI), topographic position index (TPI), peak ground motion, distance to active faults, vegetation coverage, distance to roads, lithology, and annual rainfall to establish the LR model. Based on the probabilistic seismic hazard analysis (PSHA) method, the distribution of predicted seismic motion under four earthquake scenarios is calculated including frequent, occasional, rare, and very rare earthquake occurrence. Using the PGA distribution of the four scenarios as input peak ground motion parameters, we calculated the occurrence probability of coseismic landslides in the entire Aba Prefecture and Chengdu Plain region under the action of different ground motions. The result shows that the high-hazard areas are mainly concentrated in the Longmenshan fault zone, and the southern area of Kangding is also a potential high-hazard area for landsliding. Meanwhile, as the probability of exceedance decreases, the probability of corresponding earthquake-induced landslides hazard probability and the area of high-hazard regions also significantly increase. Especially, the Pengguan complex rock mass in the southwest of the Longmenshan fault zone is the potential high-hazard area for coseismic landslides.
{"title":"Seismically-induced landslide probabilistic hazard mapping of Aba Prefecture and Chengdu Plain region, Sichuan Province, China for future seismic scenarios","authors":"Xiaoyi Shao, Siyuan Ma, Chong Xu, Jia Cheng, Xiwei Xu","doi":"10.1186/s40562-023-00307-5","DOIUrl":"https://doi.org/10.1186/s40562-023-00307-5","url":null,"abstract":"The purpose of this work is to carry out seismically induced landslide probabilistic hazard mapping for future seismic scenarios of Aba Prefecture and Chengdu Plain region, Sichuan Province, China. Nine earthquake events that occurred in the regions and neighboring areas are selected, which include a total of 251,260 landslide records. This work used 12 influencing factors including elevation, slope, aspect, relief, topographic wetness index (TWI), topographic position index (TPI), peak ground motion, distance to active faults, vegetation coverage, distance to roads, lithology, and annual rainfall to establish the LR model. Based on the probabilistic seismic hazard analysis (PSHA) method, the distribution of predicted seismic motion under four earthquake scenarios is calculated including frequent, occasional, rare, and very rare earthquake occurrence. Using the PGA distribution of the four scenarios as input peak ground motion parameters, we calculated the occurrence probability of coseismic landslides in the entire Aba Prefecture and Chengdu Plain region under the action of different ground motions. The result shows that the high-hazard areas are mainly concentrated in the Longmenshan fault zone, and the southern area of Kangding is also a potential high-hazard area for landsliding. Meanwhile, as the probability of exceedance decreases, the probability of corresponding earthquake-induced landslides hazard probability and the area of high-hazard regions also significantly increase. Especially, the Pengguan complex rock mass in the southwest of the Longmenshan fault zone is the potential high-hazard area for coseismic landslides. ","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"107 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138542651","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 : 2023-11-23DOI: 10.1186/s40562-023-00309-3
Wenrong Bai, Hailong Liu, Pengfei Lin, Xichen Li, Fan Wang
The reasons for large discrepancies between observations and simulations, as well as for uncertainties in projections of the equatorial Pacific zonal sea surface temperature (SST) gradient, are controversial. We used CMIP6 models and large ensemble simulations to show that model bias and internal variabilities affected, i.e., strengthened, the SST gradient between 1981 and 2010. The underestimation of strengthened trends in the southeast trade wind belt, the insufficient cooling effect of eastern Pacific upwelling, and the excessive westward extension of the climatological cold tongue in models jointly caused a weaker SST gradient than the recent observations. The phase transformation of the Interdecadal Pacific Oscillation (IPO) could explain ~ 51% of the observed SST gradient strengthening. After adjusting the random IPO phase to the observed IPO change, the adjusted SST gradient trends were closer to observations. We further constrained the projection of SST gradient change by using climate models’ ability to reproduce the historical SST gradient intensification or the phase of the IPO. These models suggest a weakened SST gradient in the middle of the twenty-first century.
{"title":"Reconciling opposite trends in the observed and simulated equatorial Pacific zonal sea surface temperature gradient","authors":"Wenrong Bai, Hailong Liu, Pengfei Lin, Xichen Li, Fan Wang","doi":"10.1186/s40562-023-00309-3","DOIUrl":"https://doi.org/10.1186/s40562-023-00309-3","url":null,"abstract":"The reasons for large discrepancies between observations and simulations, as well as for uncertainties in projections of the equatorial Pacific zonal sea surface temperature (SST) gradient, are controversial. We used CMIP6 models and large ensemble simulations to show that model bias and internal variabilities affected, i.e., strengthened, the SST gradient between 1981 and 2010. The underestimation of strengthened trends in the southeast trade wind belt, the insufficient cooling effect of eastern Pacific upwelling, and the excessive westward extension of the climatological cold tongue in models jointly caused a weaker SST gradient than the recent observations. The phase transformation of the Interdecadal Pacific Oscillation (IPO) could explain ~ 51% of the observed SST gradient strengthening. After adjusting the random IPO phase to the observed IPO change, the adjusted SST gradient trends were closer to observations. We further constrained the projection of SST gradient change by using climate models’ ability to reproduce the historical SST gradient intensification or the phase of the IPO. These models suggest a weakened SST gradient in the middle of the twenty-first century.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"54 13","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138496713","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 : 2023-11-22DOI: 10.1186/s40562-023-00310-w
Chia-Jeng Chen, Min-Hung Chi, Jing-Ru Ye
Modeling techniques provide a straightforward means to dissect regional hydroclimate in response to changes in land use conditions. This study uses the Weather Research and Forecasting Model (WRF) and WRF-Hydrological modeling system (WRF-Hydro), driven by survey-based land use data in 1995 and 2015, to assess how central Taiwan’s hydroclimate responds to land use/cover change. We first run WRF-Hydro with observed rainfall as meteorological forcing to ensure reasonable runoff simulation, and then select ten cases under weak synoptic forcings in July and August in recent decades for the simulation under two land use conditions. The WRF-only simulation (i.e., uncoupled with WRF-Hydro) can reveal significant changes in heat fluxes and surface variables due to land use/cover change, including sensible and latent heat fluxes, 2-m temperature and specific humidity, and precipitation over the hotspots of urbanization or downwind areas. Coupling WRF with WRF-Hydro discloses varied runoff characteristics subject to land use/cover change: a general increase in average peak flow (~ 4.3%) and total runoff volume (~ 5.0%) accompanied by less definite time-to-peak flow, indicating a synergistic but sometimes competitive relationship between the pure hydrologic/hydraulic perspective and land–atmosphere interactions. By taking the difference between the uncoupled and coupled simulations, we verify that surface pressure, precipitation, and soil moisture are more sensitive to a better depiction of terrestrial hydrological processes; differences in the spatial variances of soil moisture can be as high as two orders of magnitude. Our findings highlight the importance of more comprehensive model physics in regional hydroclimate modeling.
{"title":"Assessing hydroclimate response to land use/cover change using coupled atmospheric-hydrological models","authors":"Chia-Jeng Chen, Min-Hung Chi, Jing-Ru Ye","doi":"10.1186/s40562-023-00310-w","DOIUrl":"https://doi.org/10.1186/s40562-023-00310-w","url":null,"abstract":"Modeling techniques provide a straightforward means to dissect regional hydroclimate in response to changes in land use conditions. This study uses the Weather Research and Forecasting Model (WRF) and WRF-Hydrological modeling system (WRF-Hydro), driven by survey-based land use data in 1995 and 2015, to assess how central Taiwan’s hydroclimate responds to land use/cover change. We first run WRF-Hydro with observed rainfall as meteorological forcing to ensure reasonable runoff simulation, and then select ten cases under weak synoptic forcings in July and August in recent decades for the simulation under two land use conditions. The WRF-only simulation (i.e., uncoupled with WRF-Hydro) can reveal significant changes in heat fluxes and surface variables due to land use/cover change, including sensible and latent heat fluxes, 2-m temperature and specific humidity, and precipitation over the hotspots of urbanization or downwind areas. Coupling WRF with WRF-Hydro discloses varied runoff characteristics subject to land use/cover change: a general increase in average peak flow (~ 4.3%) and total runoff volume (~ 5.0%) accompanied by less definite time-to-peak flow, indicating a synergistic but sometimes competitive relationship between the pure hydrologic/hydraulic perspective and land–atmosphere interactions. By taking the difference between the uncoupled and coupled simulations, we verify that surface pressure, precipitation, and soil moisture are more sensitive to a better depiction of terrestrial hydrological processes; differences in the spatial variances of soil moisture can be as high as two orders of magnitude. Our findings highlight the importance of more comprehensive model physics in regional hydroclimate modeling.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"55 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138496712","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 : 2023-11-19DOI: 10.1186/s40562-023-00308-4
Saif Ullah, Mohammed Y. Ali, Muhammad A. Iqbal, Fateh Bouchaala, Hakim Saibi
The United Arab Emirates (UAE) is dependent on desalinated water and shallow aquifers to satisfy its freshwater requirements. Despite the paramount importance of understanding the depth and spatial extent of these aquifers, comprehensive investigations into the properties of these aquifers, as well as the underlying subsurface structures and stratigraphy, have been conspicuously lacking. This study presents the findings of integrated geophysical and borehole investigations conducted in the Al Jaww Plain, southeastern Al Ain, UAE, focusing on the properties of groundwater aquifers, the Semail ophiolite contact, and subsurface structures and stratigraphy. Through the analysis of groundwater borehole data, three interconnected types of groundwater aquifers have been identified, and characterized by their hydrogeological properties. The near-surface Quaternary unconfined aquifer, with an average thickness of 25 m, represents a fresh groundwater aquifer. The second aquifer, with an average thickness of 110 m, is connected to the upper Quaternary freshwater aquifer and is interpreted as part of the surficial aquifer system. The third aquifer has an average thickness of 200 m. By employing electrical resistivity tomography, the depth of the water table and groundwater potential in the shallow unconfined Quaternary aquifer near Jabal Mundassa have been estimated, aligning with the properties observed in the unconfined Quaternary aquifer across the entire Al Jaww Plain as depicted in the groundwater borehole cross section. In addition, this study provides insights into subsurface structures and stratigraphic features, revealing the westward extension of the Hawasina thrust sheet within the plain. Gravity and magnetic data analyses in the southeastern region of the Al Jaww Plain delineate the extent of the Semail ophiolite. Notably, magnetic data reveals the presence of an NW–SE-oriented magnetic anomaly detached from the main ophiolite thrust, which corresponds to the interpretation of the Semail ophiolite contact with sedimentary carbonate rocks on the Bouguer gravity map.
{"title":"Structures and stratigraphy of Al Jaww Plain, southeastern Al Ain, United Arab Emirates: implications for aquifer systems and mantle thrust sheet","authors":"Saif Ullah, Mohammed Y. Ali, Muhammad A. Iqbal, Fateh Bouchaala, Hakim Saibi","doi":"10.1186/s40562-023-00308-4","DOIUrl":"https://doi.org/10.1186/s40562-023-00308-4","url":null,"abstract":"The United Arab Emirates (UAE) is dependent on desalinated water and shallow aquifers to satisfy its freshwater requirements. Despite the paramount importance of understanding the depth and spatial extent of these aquifers, comprehensive investigations into the properties of these aquifers, as well as the underlying subsurface structures and stratigraphy, have been conspicuously lacking. This study presents the findings of integrated geophysical and borehole investigations conducted in the Al Jaww Plain, southeastern Al Ain, UAE, focusing on the properties of groundwater aquifers, the Semail ophiolite contact, and subsurface structures and stratigraphy. Through the analysis of groundwater borehole data, three interconnected types of groundwater aquifers have been identified, and characterized by their hydrogeological properties. The near-surface Quaternary unconfined aquifer, with an average thickness of 25 m, represents a fresh groundwater aquifer. The second aquifer, with an average thickness of 110 m, is connected to the upper Quaternary freshwater aquifer and is interpreted as part of the surficial aquifer system. The third aquifer has an average thickness of 200 m. By employing electrical resistivity tomography, the depth of the water table and groundwater potential in the shallow unconfined Quaternary aquifer near Jabal Mundassa have been estimated, aligning with the properties observed in the unconfined Quaternary aquifer across the entire Al Jaww Plain as depicted in the groundwater borehole cross section. In addition, this study provides insights into subsurface structures and stratigraphic features, revealing the westward extension of the Hawasina thrust sheet within the plain. Gravity and magnetic data analyses in the southeastern region of the Al Jaww Plain delineate the extent of the Semail ophiolite. Notably, magnetic data reveals the presence of an NW–SE-oriented magnetic anomaly detached from the main ophiolite thrust, which corresponds to the interpretation of the Semail ophiolite contact with sedimentary carbonate rocks on the Bouguer gravity map.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"55 2","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138496711","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 : 2023-11-13DOI: 10.1186/s40562-023-00306-6
Katsuichiro Goda
Abstract Earthquake occurrence modeling of large subduction events involves significant uncertainty, stemming from the scarcity of geological data and inaccuracy of dating techniques. The previous research on statistical modeling of full-margin ruptures of the Cascadia subduction zone attempted to address these issues. However, the adopted resampling method to account for the uncertain marine turbidite age data from the Cascadia subduction zone was not sufficient in the sample size. This study presents a statistical approach based on the Gaussian mixture model applied to significantly larger resampled Cascadia age data. The results suggest that the 3-component Gaussian mixture model outperforms the 2-component Gaussian mixture model and the 1-component renewal models by capturing the long gap and short-term clustering. The developed Gaussian mixture model is well suited to apply to probabilistic seismic and tsunami hazard analysis and the calculation of long-term probability of the future full-margin Cascadia events by considering the elapsed time since the last event.
{"title":"Statistical characterization of full-margin rupture recurrence for Cascadia subduction zone using event time resampling and Gaussian mixture model","authors":"Katsuichiro Goda","doi":"10.1186/s40562-023-00306-6","DOIUrl":"https://doi.org/10.1186/s40562-023-00306-6","url":null,"abstract":"Abstract Earthquake occurrence modeling of large subduction events involves significant uncertainty, stemming from the scarcity of geological data and inaccuracy of dating techniques. The previous research on statistical modeling of full-margin ruptures of the Cascadia subduction zone attempted to address these issues. However, the adopted resampling method to account for the uncertain marine turbidite age data from the Cascadia subduction zone was not sufficient in the sample size. This study presents a statistical approach based on the Gaussian mixture model applied to significantly larger resampled Cascadia age data. The results suggest that the 3-component Gaussian mixture model outperforms the 2-component Gaussian mixture model and the 1-component renewal models by capturing the long gap and short-term clustering. The developed Gaussian mixture model is well suited to apply to probabilistic seismic and tsunami hazard analysis and the calculation of long-term probability of the future full-margin Cascadia events by considering the elapsed time since the last event.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"62 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136281874","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 : 2023-11-04DOI: 10.1186/s40562-023-00305-7
Malte F. Stuecker
Abstract Climate variability has distinct spatial patterns with the strongest signal of sea surface temperature (SST) variance residing in the tropical Pacific. This interannual climate phenomenon, the El Niño-Southern Oscillation (ENSO), impacts weather patterns across the globe via atmospheric teleconnections. Pronounced SST variability, albeit of smaller amplitude, also exists in the other tropical basins as well as in the extratropical regions. To improve our physical understanding of internal climate variability across the global oceans, we here make the case for a conceptual model hierarchy that captures the essence of observed SST variability from subseasonal to decadal timescales. The building blocks consist of the classic stochastic climate model formulated by Klaus Hasselmann, a deterministic low-order model for ENSO variability, and the effect of the seasonal cycle on both of these models. This model hierarchy allows us to trace the impacts of seasonal processes on the statistics of observed and simulated climate variability. One of the important outcomes of ENSO’s interaction with the seasonal cycle is the generation of a frequency cascade leading to deterministic climate variability on a wide range of timescales, including the near-annual ENSO Combination Mode. Using the aforementioned building blocks, we arrive at a succinct conceptual model that delineates ENSO’s ubiquitous climate impacts and allows us to revisit ENSO’s observed statistical relationships with other coherent spatio-temporal patterns of climate variability—so called empirical modes of variability . We demonstrate the importance of correctly accounting for different seasonal phasing in the linear growth/damping rates of different climate phenomena, as well as the seasonal phasing of ENSO teleconnections and of atmospheric noise forcings. We discuss how previously some of ENSO’s relationships with other modes of variability have been misinterpreted due to non-intuitive seasonal cycle effects on both power spectra and lead/lag correlations. Furthermore, it is evident that ENSO’s impacts on climate variability outside the tropical Pacific are oftentimes larger than previously recognized and that accurately accounting for them has important implications. For instance, it has been shown that improved seasonal prediction skill can be achieved in the Indian Ocean by fully accounting for ENSO’s seasonally modulated and temporally integrated remote impacts. These results move us to refocus our attention to the tropical Pacific for understanding global patterns of climate variability and their predictability.
{"title":"The climate variability trio: stochastic fluctuations, El Niño, and the seasonal cycle","authors":"Malte F. Stuecker","doi":"10.1186/s40562-023-00305-7","DOIUrl":"https://doi.org/10.1186/s40562-023-00305-7","url":null,"abstract":"Abstract Climate variability has distinct spatial patterns with the strongest signal of sea surface temperature (SST) variance residing in the tropical Pacific. This interannual climate phenomenon, the El Niño-Southern Oscillation (ENSO), impacts weather patterns across the globe via atmospheric teleconnections. Pronounced SST variability, albeit of smaller amplitude, also exists in the other tropical basins as well as in the extratropical regions. To improve our physical understanding of internal climate variability across the global oceans, we here make the case for a conceptual model hierarchy that captures the essence of observed SST variability from subseasonal to decadal timescales. The building blocks consist of the classic stochastic climate model formulated by Klaus Hasselmann, a deterministic low-order model for ENSO variability, and the effect of the seasonal cycle on both of these models. This model hierarchy allows us to trace the impacts of seasonal processes on the statistics of observed and simulated climate variability. One of the important outcomes of ENSO’s interaction with the seasonal cycle is the generation of a frequency cascade leading to deterministic climate variability on a wide range of timescales, including the near-annual ENSO Combination Mode. Using the aforementioned building blocks, we arrive at a succinct conceptual model that delineates ENSO’s ubiquitous climate impacts and allows us to revisit ENSO’s observed statistical relationships with other coherent spatio-temporal patterns of climate variability—so called empirical modes of variability . We demonstrate the importance of correctly accounting for different seasonal phasing in the linear growth/damping rates of different climate phenomena, as well as the seasonal phasing of ENSO teleconnections and of atmospheric noise forcings. We discuss how previously some of ENSO’s relationships with other modes of variability have been misinterpreted due to non-intuitive seasonal cycle effects on both power spectra and lead/lag correlations. Furthermore, it is evident that ENSO’s impacts on climate variability outside the tropical Pacific are oftentimes larger than previously recognized and that accurately accounting for them has important implications. For instance, it has been shown that improved seasonal prediction skill can be achieved in the Indian Ocean by fully accounting for ENSO’s seasonally modulated and temporally integrated remote impacts. These results move us to refocus our attention to the tropical Pacific for understanding global patterns of climate variability and their predictability.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"9 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135773688","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 : 2023-10-20DOI: 10.1186/s40562-023-00304-8
Mohammad Heidarzadeh, Aditya Riadi Gusman, Iyan E. Mulia
Abstract This paper presents the first example of how to systematically identify the submarine landslide source of a tsunami using an innovative hybrid approach. This ground-breaking method is developed to resolve the puzzle around the source mechanism of the mysterious tsunami observed on 6th February 2023 in the Eastern Mediterranean Sea. The tsunami followed the two inland M w 7.8 and M w 7.5 Türkiye–Syria earthquakes, which occurred consequently with a 9 h interval on this day. The first earthquake (M w 7.8) had an epicentral distance of 90 km from the nearest coast, which is closer than the second one (M w 7.5) to the coast and yet its crustal deformation was almost entirely limited to inland. Therefore, the co-seismic surface displacement generated by the earthquake was ruled out as the source of the tsunami, confirmed by numerical modelling. Here, we hypothesized that the tsunami was most likely generated by a submarine landslide triggered by the earthquake. Analysis of tide gauge observations revealed that the waves arrived from 27 min to 48 min after the first earthquake (M w 7.8) at different coastal locations, implying that the potential submarine landslide was triggered by the first earthquake (M w 7.8). Backward tsunami travel time mapping using tide gauge observations guided us to constrain the area of the potential landslide. We approximated the dimensions of the landslide using spectral analysis of the tsunami observations. Consequently, an iterative trial-and-error approach was employed to confirm the landslide source of the tsunami by defining various informed alternative landslide scenarios and applying numerical modeling. Modelling showed that a submarine landslide can reproduce the tsunami observations reasonably well. It is located on a steep slope of the seafloor approximately 50 km from Arsuz. The submarine landslide is estimated to have caused a seafloor deformation measuring approximately 16 km in length and 4.0 km in width.
{"title":"The landslide source of the eastern Mediterranean tsunami on 6 February 2023 following the Mw 7.8 Kahramanmaraş (Türkiye) inland earthquake","authors":"Mohammad Heidarzadeh, Aditya Riadi Gusman, Iyan E. Mulia","doi":"10.1186/s40562-023-00304-8","DOIUrl":"https://doi.org/10.1186/s40562-023-00304-8","url":null,"abstract":"Abstract This paper presents the first example of how to systematically identify the submarine landslide source of a tsunami using an innovative hybrid approach. This ground-breaking method is developed to resolve the puzzle around the source mechanism of the mysterious tsunami observed on 6th February 2023 in the Eastern Mediterranean Sea. The tsunami followed the two inland M w 7.8 and M w 7.5 Türkiye–Syria earthquakes, which occurred consequently with a 9 h interval on this day. The first earthquake (M w 7.8) had an epicentral distance of 90 km from the nearest coast, which is closer than the second one (M w 7.5) to the coast and yet its crustal deformation was almost entirely limited to inland. Therefore, the co-seismic surface displacement generated by the earthquake was ruled out as the source of the tsunami, confirmed by numerical modelling. Here, we hypothesized that the tsunami was most likely generated by a submarine landslide triggered by the earthquake. Analysis of tide gauge observations revealed that the waves arrived from 27 min to 48 min after the first earthquake (M w 7.8) at different coastal locations, implying that the potential submarine landslide was triggered by the first earthquake (M w 7.8). Backward tsunami travel time mapping using tide gauge observations guided us to constrain the area of the potential landslide. We approximated the dimensions of the landslide using spectral analysis of the tsunami observations. Consequently, an iterative trial-and-error approach was employed to confirm the landslide source of the tsunami by defining various informed alternative landslide scenarios and applying numerical modeling. Modelling showed that a submarine landslide can reproduce the tsunami observations reasonably well. It is located on a steep slope of the seafloor approximately 50 km from Arsuz. The submarine landslide is estimated to have caused a seafloor deformation measuring approximately 16 km in length and 4.0 km in width.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135616360","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 : 2023-10-18DOI: 10.1186/s40562-023-00303-9
Kan-Hsi Hsiung, Toshiya Kanamatsu, Ken Ikehara, Masafumi Murayama, Yuhji Yamamoto
Abstract The southwestern Ryukyu Trench is an ideal place for investigating sediment transport from the Taiwan mountain belt to the Ryukyu Trench floor. To study the characteristics of trench turbidites and sediment transport along the trench, we utilize two piston cores: KR1518-PC04/PL04 at the southwestern end of Ryukyu Trench and YK1501-PC14/PL14 in the trench floor. We also collect two push cores, YK1611-6K1467MG and 6K1467MR, from undisturbed seabed surface to observe lithology. Our analysis reveals that the lithology of the cores shows homogeneous gray mud layers intercalated with very-thin fine sand layers, which we interpret as hemipelagites intercalated with very-thin turbidites. We identify 60 turbidites (0.3–4.0 cm thick) from YK1501-PC14 and 36 turbidites (0.9–4.2 cm thick) from KR1518-PC04. Based on observation from YK1501-PC14, most turbidites, which were less than 1 cm in thickness, displayed planar and sharp bottom contacts. The turbidite thickness of YK1501-PC14 (6448 m water depth) is thinner than that of KR1518-PC04 (6147 m water depth) in general. Through X-ray fluorescence core scans (ITRAX), we distinguished trench turbidites by elemental patterns and accurately determined the depths of every very-thin turbidite. Most hemipelagites from YK1501-PC14 and KR1518-PC04 show similar ITRAX profiles, indicating a similar source of the sediments. ITRAX analysis also revealed five intervals in high-Ca mud in YK1501-PC14, suggesting another potential source from the Ryukyu forearc. Anisotropy of Magnetic Susceptibility (AMS) results show that both YK1501-PC14/PL14 and KR1518-PC04/PL04 exhibit an oblate fabric indicating a normal sedimentary condition. Magnetic signatures showed the presence of pyrrhotite, supporting evidence that Taiwan-sourced sediments can be transported up to ~ 250 km by turbidity currents and spread from the Taiwan Island to the Ryukyu Trench floor. This study improves our understanding of Ryukyu Trench turbidites and provides valuable insights into active sediment transport along the southwestern Ryukyu Trench.
{"title":"Active sediment transport along trench axis: insights from X-ray fluorescence core scanning and magnetic analysis of marine sediments in the southwestern Ryukyu Trench","authors":"Kan-Hsi Hsiung, Toshiya Kanamatsu, Ken Ikehara, Masafumi Murayama, Yuhji Yamamoto","doi":"10.1186/s40562-023-00303-9","DOIUrl":"https://doi.org/10.1186/s40562-023-00303-9","url":null,"abstract":"Abstract The southwestern Ryukyu Trench is an ideal place for investigating sediment transport from the Taiwan mountain belt to the Ryukyu Trench floor. To study the characteristics of trench turbidites and sediment transport along the trench, we utilize two piston cores: KR1518-PC04/PL04 at the southwestern end of Ryukyu Trench and YK1501-PC14/PL14 in the trench floor. We also collect two push cores, YK1611-6K1467MG and 6K1467MR, from undisturbed seabed surface to observe lithology. Our analysis reveals that the lithology of the cores shows homogeneous gray mud layers intercalated with very-thin fine sand layers, which we interpret as hemipelagites intercalated with very-thin turbidites. We identify 60 turbidites (0.3–4.0 cm thick) from YK1501-PC14 and 36 turbidites (0.9–4.2 cm thick) from KR1518-PC04. Based on observation from YK1501-PC14, most turbidites, which were less than 1 cm in thickness, displayed planar and sharp bottom contacts. The turbidite thickness of YK1501-PC14 (6448 m water depth) is thinner than that of KR1518-PC04 (6147 m water depth) in general. Through X-ray fluorescence core scans (ITRAX), we distinguished trench turbidites by elemental patterns and accurately determined the depths of every very-thin turbidite. Most hemipelagites from YK1501-PC14 and KR1518-PC04 show similar ITRAX profiles, indicating a similar source of the sediments. ITRAX analysis also revealed five intervals in high-Ca mud in YK1501-PC14, suggesting another potential source from the Ryukyu forearc. Anisotropy of Magnetic Susceptibility (AMS) results show that both YK1501-PC14/PL14 and KR1518-PC04/PL04 exhibit an oblate fabric indicating a normal sedimentary condition. Magnetic signatures showed the presence of pyrrhotite, supporting evidence that Taiwan-sourced sediments can be transported up to ~ 250 km by turbidity currents and spread from the Taiwan Island to the Ryukyu Trench floor. This study improves our understanding of Ryukyu Trench turbidites and provides valuable insights into active sediment transport along the southwestern Ryukyu Trench.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135884421","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}
Abstract Although Myanmar is an earthquake-prone country, there has not been proposed an official national seismic hazard map. Thus, this study conducted a probabilistic seismic hazard assessment for Myanmar and some of its metropolitan areas. Performing this assessment required a set of databases that incorporates both earthquake catalogs and fault parameters. We obtained seismic parameters from the International Seismological Centre, and the fault database includes fault parameters from paper reviews and the database. Based on seismic activities, we considered three categories of seismogenic sources—active fault source, shallow area source, and subduction zone source. We evaluated seismic activity of each source based on the earthquake catalogs and fault parameters. Evaluating the ground-shaking behaviors for Myanmar requires evaluation of ground-shaking attenuation; therefore, we validated existing ground motion prediction equations (GMPEs) by comparing instrumental observations and felt intensities for recent earthquakes. We then incorporated the best fitting GMPEs into our seismic hazard assessments. By incorporating the V s 30 (the average shear velocity down to 30 m depth) map from an analysis of topographic slope, we utilized site effect and assessed national probabilistic seismic hazards for Myanmar. The assessment shows highest seismic hazard levels near those faults with high slip rates, including the Sagaing Fault and along the Western Coast of Myanmar. We also assessed seismic hazard for some metropolitan cities, including Bagan, Bago, Mandalay, Sagaing, Taungoo and Yangon, in the forms of hazard curves and disaggregation by implementing detailed V s 30 maps from micro-tremor surveys. The city-scale assessments show higher hazards for sites close to an active fault or/and with a low V s 30 , demonstrating the importance of investigating site conditions. The outcomes of this study will be beneficial to urban planning on a city scale and building code legislation on a national scale.
{"title":"Probabilistic seismic hazard assessments for Myanmar and its metropolitan areas","authors":"Huan-Bin Yang, Yuan-Kai Chang, Wei Liu, Guan-Yi Sung, Jia-Cian Gao, Myo Thant, Phyo Maung Maung, Chung-Han Chan","doi":"10.1186/s40562-023-00301-x","DOIUrl":"https://doi.org/10.1186/s40562-023-00301-x","url":null,"abstract":"Abstract Although Myanmar is an earthquake-prone country, there has not been proposed an official national seismic hazard map. Thus, this study conducted a probabilistic seismic hazard assessment for Myanmar and some of its metropolitan areas. Performing this assessment required a set of databases that incorporates both earthquake catalogs and fault parameters. We obtained seismic parameters from the International Seismological Centre, and the fault database includes fault parameters from paper reviews and the database. Based on seismic activities, we considered three categories of seismogenic sources—active fault source, shallow area source, and subduction zone source. We evaluated seismic activity of each source based on the earthquake catalogs and fault parameters. Evaluating the ground-shaking behaviors for Myanmar requires evaluation of ground-shaking attenuation; therefore, we validated existing ground motion prediction equations (GMPEs) by comparing instrumental observations and felt intensities for recent earthquakes. We then incorporated the best fitting GMPEs into our seismic hazard assessments. By incorporating the V s 30 (the average shear velocity down to 30 m depth) map from an analysis of topographic slope, we utilized site effect and assessed national probabilistic seismic hazards for Myanmar. The assessment shows highest seismic hazard levels near those faults with high slip rates, including the Sagaing Fault and along the Western Coast of Myanmar. We also assessed seismic hazard for some metropolitan cities, including Bagan, Bago, Mandalay, Sagaing, Taungoo and Yangon, in the forms of hazard curves and disaggregation by implementing detailed V s 30 maps from micro-tremor surveys. The city-scale assessments show higher hazards for sites close to an active fault or/and with a low V s 30 , demonstrating the importance of investigating site conditions. The outcomes of this study will be beneficial to urban planning on a city scale and building code legislation on a national scale.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135803336","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 : 2023-10-13DOI: 10.1186/s40562-023-00302-w
Gabriella Alodia, None Nurhidayat, Dyan P. Sobarudin, Dian Adrianto, Angga Dwinovantyo, Steven Solikin, Mustafa Hanafi, Astyka Pamumpuni, Idham A. Kurniawan, None Poerbandono, Chris M. Green, Andrew M. McCaig
Abstract An expedition to confirm the presence of underwater hazards was carried out in Halmahera waters, Indonesia, to the west of Halmahera Island from August to September 2021. The expedition carried out a multibeam survey, surface-towed magnetic survey, and seafloor sampling. A ~ 615-m-tall conical feature with traces of hydrothermal activity was discovered. The feature is bounded on the southeastern (SE) side by a series of normal faults at the peak, with possible dextral strike-slip faults traced west of the feature. The feature displays the potential presence of volcanic rocks based on the observed contrasting magnetic anomaly signature of down to − 100 nT, which at the magnetic equator corresponds to the presence of highly magnetised material. Four 2.5-D magnetic models were built to test various scenarios on the subsurface structure of the feature, mainly focusing on the presence of volcanic rocks at different epochs and a possible presence of serpentinisation. X-ray diffraction (XRD) of the silt and clay sediments sampled confirms traces of late-stage hydrothermal activity, indicated by a high percentage of quartz (53.87%), followed by calcite (34.56%), kaolinite (6.54%), and illite minerals (5.04%). Non-carbonate materials are yet to be found in the sampled sand and gravel sediments, which mainly consist of shell and coral fragments. The discovery of the conical feature, now termed the Yudo Sagoro Hill, provides new information on the structure and activities on the seafloor of Halmahera waters.
{"title":"Discovery of a conical feature in Halmahera waters, Indonesia: traces of a late-stage hydrothermal activity","authors":"Gabriella Alodia, None Nurhidayat, Dyan P. Sobarudin, Dian Adrianto, Angga Dwinovantyo, Steven Solikin, Mustafa Hanafi, Astyka Pamumpuni, Idham A. Kurniawan, None Poerbandono, Chris M. Green, Andrew M. McCaig","doi":"10.1186/s40562-023-00302-w","DOIUrl":"https://doi.org/10.1186/s40562-023-00302-w","url":null,"abstract":"Abstract An expedition to confirm the presence of underwater hazards was carried out in Halmahera waters, Indonesia, to the west of Halmahera Island from August to September 2021. The expedition carried out a multibeam survey, surface-towed magnetic survey, and seafloor sampling. A ~ 615-m-tall conical feature with traces of hydrothermal activity was discovered. The feature is bounded on the southeastern (SE) side by a series of normal faults at the peak, with possible dextral strike-slip faults traced west of the feature. The feature displays the potential presence of volcanic rocks based on the observed contrasting magnetic anomaly signature of down to − 100 nT, which at the magnetic equator corresponds to the presence of highly magnetised material. Four 2.5-D magnetic models were built to test various scenarios on the subsurface structure of the feature, mainly focusing on the presence of volcanic rocks at different epochs and a possible presence of serpentinisation. X-ray diffraction (XRD) of the silt and clay sediments sampled confirms traces of late-stage hydrothermal activity, indicated by a high percentage of quartz (53.87%), followed by calcite (34.56%), kaolinite (6.54%), and illite minerals (5.04%). Non-carbonate materials are yet to be found in the sampled sand and gravel sediments, which mainly consist of shell and coral fragments. The discovery of the conical feature, now termed the Yudo Sagoro Hill, provides new information on the structure and activities on the seafloor of Halmahera waters.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"255 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135858765","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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