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}
Pub Date : 2023-10-10DOI: 10.1186/s40562-023-00300-y
Wen-Bin Doo, Chung-Liang Lo, Yin-Sheng Huang, Wen-Nan Wu, Shiou-Ya Wang
Abstract The Ryukyu trench-arc-back arc system is part of the subduction margins of the Philippine Sea plate. Previous studies have indicated that several geophysical and geological characteristics reveal significant variations (including convergent rate, topography, subducting slab angle etc.) along this subduction system. In addition, the strength of plate coupling and the potential of large earthquake occurrence in the Ryukyu subduction zone have been major subjects of debate for decades. To gain new insights into the spatial variations in the crustal structure and strength of plate coupling along the Ryukyu subduction zone, in the present study, based on three P-wave seismic velocity profiles, we construct density models for 2-D gravity modeling. Then, we estimate the mantle lithosphere buoyancy (H m ) using these three density models to determine the strength of plate coupling between the subducting Philippine Sea plate and the overriding Eurasian plate, which could provide information for evaluating large earthquakes potential. 2-D gravity modeling results reveal that oceanic plateaus and/or submarine ridges with obviously less dense and thick oceanic crust are subducting in the northern and central parts of the Ryukyu Trench, which could increase the slab buoyancy in these regions. The H m results indicate that the strength of plate coupling is almost weak in the north and is relatively strong in the central Ryukyu subduction zone.
{"title":"Variations in the crustal structure and strength of plate coupling along the Ryukyu subduction zone","authors":"Wen-Bin Doo, Chung-Liang Lo, Yin-Sheng Huang, Wen-Nan Wu, Shiou-Ya Wang","doi":"10.1186/s40562-023-00300-y","DOIUrl":"https://doi.org/10.1186/s40562-023-00300-y","url":null,"abstract":"Abstract The Ryukyu trench-arc-back arc system is part of the subduction margins of the Philippine Sea plate. Previous studies have indicated that several geophysical and geological characteristics reveal significant variations (including convergent rate, topography, subducting slab angle etc.) along this subduction system. In addition, the strength of plate coupling and the potential of large earthquake occurrence in the Ryukyu subduction zone have been major subjects of debate for decades. To gain new insights into the spatial variations in the crustal structure and strength of plate coupling along the Ryukyu subduction zone, in the present study, based on three P-wave seismic velocity profiles, we construct density models for 2-D gravity modeling. Then, we estimate the mantle lithosphere buoyancy (H m ) using these three density models to determine the strength of plate coupling between the subducting Philippine Sea plate and the overriding Eurasian plate, which could provide information for evaluating large earthquakes potential. 2-D gravity modeling results reveal that oceanic plateaus and/or submarine ridges with obviously less dense and thick oceanic crust are subducting in the northern and central parts of the Ryukyu Trench, which could increase the slab buoyancy in these regions. The H m results indicate that the strength of plate coupling is almost weak in the north and is relatively strong in the central Ryukyu subduction zone.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136356672","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 : 2023-09-30DOI: 10.1186/s40562-023-00299-2
Lei Li, Tao Chen, Chao Shen, Shuo Ti, Shihan Wang, Chunlin Cai, Wen Li, Jing Luo
Abstract The Earth’s electrical environment is influenced by both external and internal driving factors. Internal driving factors include the global charging current produced by lightning storms, global aerosol concentrations and cloud coverage. External factors are caused by various space weather phenomena, including changes in the Sun’s magnetic field, solar flares, coronal mass ejections, and ionization changes from high-energy particles from the Sun and galactic cosmic rays. This study focuses on the cosmic ray intensity changes observed at the OULU Station and the vertical atmospheric electric field changes observed at the Azores and Studenec stations during a solar activity event in September 2017. The results indicate that the atmospheric electric field at the two stations (Azores and Studenec) simultaneously decreased by 80% and 120% of the mean atmospheric electric field value, respectively, during the same time as the significant decrease in cosmic ray intensity. The linear correlation coefficient between the decreased atmospheric electric field measured at these two stations was 0.60, indicating a global effect from the shocks and magnetic clouds associated with coronal mass ejections on atmospheric electricity. Finally, this study describes shock waves and magnetic clouds that impede the propagation of galactic cosmic rays, resulting in a decrease in ionospheric potential and atmospheric electric field.
{"title":"Near-surface atmospheric electric field changes through magnetic clouds via coronal mass ejections","authors":"Lei Li, Tao Chen, Chao Shen, Shuo Ti, Shihan Wang, Chunlin Cai, Wen Li, Jing Luo","doi":"10.1186/s40562-023-00299-2","DOIUrl":"https://doi.org/10.1186/s40562-023-00299-2","url":null,"abstract":"Abstract The Earth’s electrical environment is influenced by both external and internal driving factors. Internal driving factors include the global charging current produced by lightning storms, global aerosol concentrations and cloud coverage. External factors are caused by various space weather phenomena, including changes in the Sun’s magnetic field, solar flares, coronal mass ejections, and ionization changes from high-energy particles from the Sun and galactic cosmic rays. This study focuses on the cosmic ray intensity changes observed at the OULU Station and the vertical atmospheric electric field changes observed at the Azores and Studenec stations during a solar activity event in September 2017. The results indicate that the atmospheric electric field at the two stations (Azores and Studenec) simultaneously decreased by 80% and 120% of the mean atmospheric electric field value, respectively, during the same time as the significant decrease in cosmic ray intensity. The linear correlation coefficient between the decreased atmospheric electric field measured at these two stations was 0.60, indicating a global effect from the shocks and magnetic clouds associated with coronal mass ejections on atmospheric electricity. Finally, this study describes shock waves and magnetic clouds that impede the propagation of galactic cosmic rays, resulting in a decrease in ionospheric potential and atmospheric electric field.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136342063","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 : 2023-09-22DOI: 10.1186/s40562-023-00298-3
Mohammad Hakim Rezayee, Mahdi Khalaj, Hideki Mizunaga
Abstract The Koh Safi Chromite Ore Deposit is located in Afghanistan’s northern–northeastern end of the Kabul–Kandahar ophiolite zone. Sedimentary formations, delayed volcanic, and ultramafic rock groups, including peridotites and serpentinites, could all have been found in the Koh Safi area, where structural discontinuities with the two trends of northwest–southeast and east–west can be identified. High-grade serpentinite units have many chromite deposits, whereas peridotite has a lot of medium-grade deposits. This paper performs a ground magnetic data analysis based on structural analysis and 3-D susceptibility inversion. The boundaries of structural faults and anomalous bodies are likely delineated in a northwest-to-southeast orientation using a series of derivative maps, including Total Horizontal Derivative, Analytical Signal, and Theta Map. For inversion, many regularization norms that included the range of smooth, intermediate, and compact models were used to examine a particular susceptibility value that occurred in a model cell. The sparse and blocky norms [0,1,1,1] were suggested for our inversion in field data based on synthetic data to determine an appropriate norm. A 3-D inversion of ground magnetic data shows that the highly magnetic zone supposed to be the host rocks seems to be where chromite occurs in the study area.
{"title":"Structural analysis and susceptibility inversion based on ground magnetic data to map the chromite mineral resources: a case study of the Koh Safi Chromite Ore Deposit, Parwan, Afghanistan","authors":"Mohammad Hakim Rezayee, Mahdi Khalaj, Hideki Mizunaga","doi":"10.1186/s40562-023-00298-3","DOIUrl":"https://doi.org/10.1186/s40562-023-00298-3","url":null,"abstract":"Abstract The Koh Safi Chromite Ore Deposit is located in Afghanistan’s northern–northeastern end of the Kabul–Kandahar ophiolite zone. Sedimentary formations, delayed volcanic, and ultramafic rock groups, including peridotites and serpentinites, could all have been found in the Koh Safi area, where structural discontinuities with the two trends of northwest–southeast and east–west can be identified. High-grade serpentinite units have many chromite deposits, whereas peridotite has a lot of medium-grade deposits. This paper performs a ground magnetic data analysis based on structural analysis and 3-D susceptibility inversion. The boundaries of structural faults and anomalous bodies are likely delineated in a northwest-to-southeast orientation using a series of derivative maps, including Total Horizontal Derivative, Analytical Signal, and Theta Map. For inversion, many regularization norms that included the range of smooth, intermediate, and compact models were used to examine a particular susceptibility value that occurred in a model cell. The sparse and blocky norms [0,1,1,1] were suggested for our inversion in field data based on synthetic data to determine an appropriate norm. A 3-D inversion of ground magnetic data shows that the highly magnetic zone supposed to be the host rocks seems to be where chromite occurs in the study area.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"154 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136060055","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 : 2023-09-07DOI: 10.1186/s40562-023-00295-6
John Chien-Han Tseng, Bo-An Tsai, Kaoshen Chung
{"title":"Sea surface temperature clustering and prediction in the Pacific Ocean based on isometric feature mapping analysis","authors":"John Chien-Han Tseng, Bo-An Tsai, Kaoshen Chung","doi":"10.1186/s40562-023-00295-6","DOIUrl":"https://doi.org/10.1186/s40562-023-00295-6","url":null,"abstract":"","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":" ","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46276715","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 : 2023-09-06DOI: 10.1186/s40562-023-00297-4
Kei Katsumata
{"title":"Slow slip event in the focal area of the 1975 Kurile tsunami earthquake inferred from unusual long-term seismic quiescence","authors":"Kei Katsumata","doi":"10.1186/s40562-023-00297-4","DOIUrl":"https://doi.org/10.1186/s40562-023-00297-4","url":null,"abstract":"","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":" ","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45980788","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 : 2023-08-29DOI: 10.1186/s40562-023-00293-8
M. T. Maulana, T. Yamazaki, T. Iwasaki, M. R. Abdillah
{"title":"Regional variation of the influence of cross-equatorial northerly surge towards diurnal cycle of rainfall over Java Island","authors":"M. T. Maulana, T. Yamazaki, T. Iwasaki, M. R. Abdillah","doi":"10.1186/s40562-023-00293-8","DOIUrl":"https://doi.org/10.1186/s40562-023-00293-8","url":null,"abstract":"","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":" ","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43559050","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 : 2023-08-25DOI: 10.1186/s40562-023-00294-7
D. Peng, Kit Ying Soon, V. Khoo, Evert Mulder, Poh Weng Wong, E. Hill
{"title":"Tidal asymmetry and transition in the Singapore Strait revealed by GNSS interferometric reflectometry","authors":"D. Peng, Kit Ying Soon, V. Khoo, Evert Mulder, Poh Weng Wong, E. Hill","doi":"10.1186/s40562-023-00294-7","DOIUrl":"https://doi.org/10.1186/s40562-023-00294-7","url":null,"abstract":"","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":" ","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41890838","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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