Shu-Kun Hsu - Academia.edu (original) (raw)
Papers by Shu-Kun Hsu
AGU Fall Meeting Abstracts, Dec 1, 2019
EGU General Assembly Conference Abstracts, Apr 1, 2019
EGU General Assembly Conference Abstracts, Apr 1, 2018
沖縄トラフ西部は,アジア大陸東縁部の活動的なリフティングの起こっている場所として知られており,背弧海盆の発達のテク トニクス・ダイナミクスを解明する上で重要な海域である。本海域に於ては,1996... more 沖縄トラフ西部は,アジア大陸東縁部の活動的なリフティングの起こっている場所として知られており,背弧海盆の発達のテク トニクス・ダイナミクスを解明する上で重要な海域である。本海域に於ては,1996年の「ラタラン」による台湾東方SPOT海域の調 査結果を受けて,2000年7月から8月に掛けて,「よこすか」・「しんかい6500」により,調査("Lequios"航海:航海番号YK00-06 Leg2)が行われた。本調査研究は,(1)沖縄トラフ中央地溝の形成・発達過程, (2)トラフ域の火山活動, (3)トラフ域の熱水活動, (4)広域テクトニクス・ダイナミクスの解明を目指すものであり,調査期間中,「しんかい6500」による潜航が10回行われた。本調査 の結果,新たに2箇所の熱水活動域が確認された。一つはSPOT域内,もう一つは宮古島北方の沖縄トラフ中軸部に位置する。 噴出する熱水の最高温度は,前者が170°C,後者が151°Cであった。双方共,熱水性の硫化物の沈殿物と化学合成生物群集を 伴うものであった。SEABEAM2112による海底地形調査の結果,中央地溝は明瞭にセグメント化していることが明らかになった。 東側の熱水活動域は2個のセグメントの境界部に位置している。また,セグメント中央部にはマグマ活動・熱水活動などの徴候は 確認されなかった。八重山中央地溝上の中央海丘は時代が古く,海丘周辺の海底は海丘の荷重による弾性変形を起こしてい る様子である。このことから,中央地溝に於てはもはやリフティングを起こしていないことが推定される。一方,SPOT域と同様,与 那国島・石垣島北方で,新たに蛇行した海底谷が確認された。これは明らかに陸上の河川の浸蝕により発達したものであり,本 海域が嘗ては陸上或いは浅海域にあって,沖縄トラフのリフティングの運動により1000m以上沈降を起こしたことが推定される。
In the northern margin of the westernmost Okinawa Trough, three obviously submarine canyons exist... more In the northern margin of the westernmost Okinawa Trough, three obviously submarine canyons exist. From east to west, they are the North Mein-Hua Submarine Canyon, Mein-Hua Submarine Canyon and the Keelung Valley. Their orientations are NW-SE across the continental margin. The Okinawa Trough is a backarc basin and is under backarc extension. To better understand the extensional tectonics, we have conducted multi-channel reflection seismics, sub-bottom profilers and multi-beam bathymetry in the westernmost area. In the east, the slope of the continental margin between the Mein-Hua Submarine Canyon and the North Mei-Hua Submarine Canyon is very gentle, implying that the current risk of major slope failure is low. However, between the Keelung Valley and the Mei-Hua Submarine Canyon, the slope is rather steep and the submarine landslide hazard may exist. Our results show two general trends of fracture or faulting. The NE-SW trending faults generally follow the major orientation of the Taiwan mountain belt. Thus, these faults could be reverse faults from the former collisional thrust faults to currently post-collisional normal faults. Secondly, the E-W trending faults are consistent with the N-S extending of the Southern Okinawa Trough. It is probably associated with the offshore extension of the Kenchiao Fault or the Sanchiao Fault. These two faults could be regarded as the headwalls of the potential large submarine landslides. However, our reflection seismic profiles do not show a clear failure surface or a decollement. It could imply that the movement type of the potential submarine landslides could be of spreads.
Tectonophysics, 2016
We have discovered in a marine core, located 20 km east of the Coastal Range of Taiwan at the top... more We have discovered in a marine core, located 20 km east of the Coastal Range of Taiwan at the top of a 1200 m deep submarine high, sheltered from rivers discharges and gravitational flows, a 23 cm-thick anomalous sequence topped with broken bivalves and wood fragments. Based on radiocarbon dating, we distinguish five sub-events within ∼100 yrs, about 3000 years ago. The oldest four sub-events are interpreted as the record of local submarine landslides, likely triggered by clustered earthquakes that are common in this tectonically active area. The last event including shells and wood has a different origin. Despite the high level of climatic and tectonic recent activity, no comparable event has been observed at the same site since that time, making it unique during the last 3.75 ka. Hydrodynamical modeling stimulated with a set of submarine landslide-triggered tsunami sources and combined with the regional oceanic circulation dominated by the Kuroshio Current, allow us to better constrain the transport paths of the suspended material, the expected run-up at the coast, and ultimately the trigger and source that best fit our observations. The Kuroshio Current appears as a strong constraint that generally prevents cross-shore transport of suspended material even during a major tsunami. Since the largest aerial debris flow observed along the east coast of Taiwan during the last 4 ka was synchronous with the marine deposit, our preferred scenario starts with the occurrence of four distinct large earthquakes within less than a century, triggering both submarine and aerial landslides in the study area. Then, a giant typhoon reworked the nearshore material as well as the slided material stored upstream resulting in a debris flow. It deeply modified the surface current, allowing the wood debris and shells to fastly reach the core site.
Multibeam echo sounder, deep-towed sidescan sonar and sub-bottom profiler surveys are carried out... more Multibeam echo sounder, deep-towed sidescan sonar and sub-bottom profiler surveys are carried out in the near shore area off SW Taiwan. Thirteen mud volcanoes are recognized by using multibeam bathymetry. The high-resolution sub-bottom profiler data show the existence of more than one hundred gas seeps and one pockmark distributed in the study area. These mud volcanoes are situated at the summit of mud diapiric structures identified by multichannel seismic reflection (MCS) profiles. It indicates that the growth of mud volcano is closely related to mud diapiric structure. The fluid source of mud volcanoes come from the diapiric structure and fluid migrates upward along fractures to the seafloor. For the first time, ROV survey for mud volcano observation is applied in the near shore area off SW Taiwan in 2011. The results of ROV observation reveal three active mud volcanoes with eruption from seafloor. The eruption cycle of mud volcanoes MV1 and MV5 are about every 3~5 minutes, and MV...
Eos, Transactions American Geophysical Union, 1997
A joint French‐Taiwanese cruise in May and June 1996 on the French research vessel L'Atalante... more A joint French‐Taiwanese cruise in May and June 1996 on the French research vessel L'Atalante has provided detailed structural images of the sea floor east and southwest of Taiwan. High quality swath bathymetry (see Figure 1) and seismic reflection profiles collected in southeastern and southwestern offshore areas near Taiwan will increase our understanding of how the Luzon Arc is deformed by its collision with the Chinese passive margin and how the Manila Trench connects with the deformation front on Taiwan. The data collected off the eastern coast of Taiwan will elucidate the nature of the plate boundary between the Ryukyu subduction zone and the Taiwan mountain belt and reveal the mode of back arc opening in the Southern Okinawa Trough. The investigations will contribute to understanding the processes of accretion of an arc to a continent prior to the ultimate collision between continents.
Geology and geophysics of an arc-continent collision, Taiwan, 2002
Marine observations offshore of Taiwan indicate intense deformation of the Luzon arc-forearc comp... more Marine observations offshore of Taiwan indicate intense deformation of the Luzon arc-forearc complex, with episodic eastward migration of the active deformation front across the complex. This active tectonic domain absorbs a significant amount of shortening between the Eurasia margin and the Philippine Sea Plate, which is moving towards N 310° E at about 8 cm/yr relative to Eurasia. Swath bathymetry and back-scattering data, together with seismic reflection and geopotential data obtained during the ACT (Active Collision in Taiwan) cruise onboard the R/V L'Atalante, showed major north to south changes in the tectonic style in both the indenting arc and the host margin. Structural observations show that the forearc basement of the Luzon arc no longer exists north of 22°30'N. To the south, only a small part of the forearc domain may remain beneath the Huatung Ridge (rear portion of the former Manila trench oceanic accretionary wedge including forearc and intra-arc sequences) and rear of the thrust wedge. A tectonic model involving the progressive underthrusting of large slices of the forearc basement may account for the contrasting styles of deformation encountered from south to north across the collisional orogen and apparent missing of the forearc region. The progressive subduction of the continental margin of China induces: 1) to the south, major eastward backthrusting and shortening of the forearc domain between the former oceanic accretionary wedge and the Luzon Arc volcanic edifice, 2) to the north, accretion of parts of the arc domain to the collisional belt associated with westward thrusting, eastward backthrusting at the base of the slope and block rotation.
The Philippine Sea Plate overrides the Eurasian Plate along the east-dipping Manila Trench betwee... more The Philippine Sea Plate overrides the Eurasian Plate along the east-dipping Manila Trench between Taiwan and Luzon islands. From south to north, the plate convergence gradually evolves from normal subduction of the South China Sea (SCS) lithosphere to initial collision of the Taiwan orogen. In order to better understand the deep crustal structures in this region, 11 multi-channel seismic reflection profiles were collected during R/V G. Langseth cruises MGL0905 and MGL0908 from April to July, 2009. The results show that large volume of sediments has accumulated in the northern Manila Trench and the oceanic crusts as thick as 10 km. Normal faults have widely distributed in the trench area due to the bending of subducting plate. The SCS basement generally deepens to the Luzon arc. Several seamounts intruded and extruded onto the volcanic SCS basement and lead to rough reliefs of the SCS basement. The rough-relief SCS basement has affected the deformation of decollement and sedimentary...
AGU Fall Meeting Abstracts, Dec 1, 2019
EGU General Assembly Conference Abstracts, Apr 1, 2019
EGU General Assembly Conference Abstracts, Apr 1, 2018
沖縄トラフ西部は,アジア大陸東縁部の活動的なリフティングの起こっている場所として知られており,背弧海盆の発達のテク トニクス・ダイナミクスを解明する上で重要な海域である。本海域に於ては,1996... more 沖縄トラフ西部は,アジア大陸東縁部の活動的なリフティングの起こっている場所として知られており,背弧海盆の発達のテク トニクス・ダイナミクスを解明する上で重要な海域である。本海域に於ては,1996年の「ラタラン」による台湾東方SPOT海域の調 査結果を受けて,2000年7月から8月に掛けて,「よこすか」・「しんかい6500」により,調査("Lequios"航海:航海番号YK00-06 Leg2)が行われた。本調査研究は,(1)沖縄トラフ中央地溝の形成・発達過程, (2)トラフ域の火山活動, (3)トラフ域の熱水活動, (4)広域テクトニクス・ダイナミクスの解明を目指すものであり,調査期間中,「しんかい6500」による潜航が10回行われた。本調査 の結果,新たに2箇所の熱水活動域が確認された。一つはSPOT域内,もう一つは宮古島北方の沖縄トラフ中軸部に位置する。 噴出する熱水の最高温度は,前者が170°C,後者が151°Cであった。双方共,熱水性の硫化物の沈殿物と化学合成生物群集を 伴うものであった。SEABEAM2112による海底地形調査の結果,中央地溝は明瞭にセグメント化していることが明らかになった。 東側の熱水活動域は2個のセグメントの境界部に位置している。また,セグメント中央部にはマグマ活動・熱水活動などの徴候は 確認されなかった。八重山中央地溝上の中央海丘は時代が古く,海丘周辺の海底は海丘の荷重による弾性変形を起こしてい る様子である。このことから,中央地溝に於てはもはやリフティングを起こしていないことが推定される。一方,SPOT域と同様,与 那国島・石垣島北方で,新たに蛇行した海底谷が確認された。これは明らかに陸上の河川の浸蝕により発達したものであり,本 海域が嘗ては陸上或いは浅海域にあって,沖縄トラフのリフティングの運動により1000m以上沈降を起こしたことが推定される。
In the northern margin of the westernmost Okinawa Trough, three obviously submarine canyons exist... more In the northern margin of the westernmost Okinawa Trough, three obviously submarine canyons exist. From east to west, they are the North Mein-Hua Submarine Canyon, Mein-Hua Submarine Canyon and the Keelung Valley. Their orientations are NW-SE across the continental margin. The Okinawa Trough is a backarc basin and is under backarc extension. To better understand the extensional tectonics, we have conducted multi-channel reflection seismics, sub-bottom profilers and multi-beam bathymetry in the westernmost area. In the east, the slope of the continental margin between the Mein-Hua Submarine Canyon and the North Mei-Hua Submarine Canyon is very gentle, implying that the current risk of major slope failure is low. However, between the Keelung Valley and the Mei-Hua Submarine Canyon, the slope is rather steep and the submarine landslide hazard may exist. Our results show two general trends of fracture or faulting. The NE-SW trending faults generally follow the major orientation of the Taiwan mountain belt. Thus, these faults could be reverse faults from the former collisional thrust faults to currently post-collisional normal faults. Secondly, the E-W trending faults are consistent with the N-S extending of the Southern Okinawa Trough. It is probably associated with the offshore extension of the Kenchiao Fault or the Sanchiao Fault. These two faults could be regarded as the headwalls of the potential large submarine landslides. However, our reflection seismic profiles do not show a clear failure surface or a decollement. It could imply that the movement type of the potential submarine landslides could be of spreads.
Tectonophysics, 2016
We have discovered in a marine core, located 20 km east of the Coastal Range of Taiwan at the top... more We have discovered in a marine core, located 20 km east of the Coastal Range of Taiwan at the top of a 1200 m deep submarine high, sheltered from rivers discharges and gravitational flows, a 23 cm-thick anomalous sequence topped with broken bivalves and wood fragments. Based on radiocarbon dating, we distinguish five sub-events within ∼100 yrs, about 3000 years ago. The oldest four sub-events are interpreted as the record of local submarine landslides, likely triggered by clustered earthquakes that are common in this tectonically active area. The last event including shells and wood has a different origin. Despite the high level of climatic and tectonic recent activity, no comparable event has been observed at the same site since that time, making it unique during the last 3.75 ka. Hydrodynamical modeling stimulated with a set of submarine landslide-triggered tsunami sources and combined with the regional oceanic circulation dominated by the Kuroshio Current, allow us to better constrain the transport paths of the suspended material, the expected run-up at the coast, and ultimately the trigger and source that best fit our observations. The Kuroshio Current appears as a strong constraint that generally prevents cross-shore transport of suspended material even during a major tsunami. Since the largest aerial debris flow observed along the east coast of Taiwan during the last 4 ka was synchronous with the marine deposit, our preferred scenario starts with the occurrence of four distinct large earthquakes within less than a century, triggering both submarine and aerial landslides in the study area. Then, a giant typhoon reworked the nearshore material as well as the slided material stored upstream resulting in a debris flow. It deeply modified the surface current, allowing the wood debris and shells to fastly reach the core site.
Multibeam echo sounder, deep-towed sidescan sonar and sub-bottom profiler surveys are carried out... more Multibeam echo sounder, deep-towed sidescan sonar and sub-bottom profiler surveys are carried out in the near shore area off SW Taiwan. Thirteen mud volcanoes are recognized by using multibeam bathymetry. The high-resolution sub-bottom profiler data show the existence of more than one hundred gas seeps and one pockmark distributed in the study area. These mud volcanoes are situated at the summit of mud diapiric structures identified by multichannel seismic reflection (MCS) profiles. It indicates that the growth of mud volcano is closely related to mud diapiric structure. The fluid source of mud volcanoes come from the diapiric structure and fluid migrates upward along fractures to the seafloor. For the first time, ROV survey for mud volcano observation is applied in the near shore area off SW Taiwan in 2011. The results of ROV observation reveal three active mud volcanoes with eruption from seafloor. The eruption cycle of mud volcanoes MV1 and MV5 are about every 3~5 minutes, and MV...
Eos, Transactions American Geophysical Union, 1997
A joint French‐Taiwanese cruise in May and June 1996 on the French research vessel L'Atalante... more A joint French‐Taiwanese cruise in May and June 1996 on the French research vessel L'Atalante has provided detailed structural images of the sea floor east and southwest of Taiwan. High quality swath bathymetry (see Figure 1) and seismic reflection profiles collected in southeastern and southwestern offshore areas near Taiwan will increase our understanding of how the Luzon Arc is deformed by its collision with the Chinese passive margin and how the Manila Trench connects with the deformation front on Taiwan. The data collected off the eastern coast of Taiwan will elucidate the nature of the plate boundary between the Ryukyu subduction zone and the Taiwan mountain belt and reveal the mode of back arc opening in the Southern Okinawa Trough. The investigations will contribute to understanding the processes of accretion of an arc to a continent prior to the ultimate collision between continents.
Geology and geophysics of an arc-continent collision, Taiwan, 2002
Marine observations offshore of Taiwan indicate intense deformation of the Luzon arc-forearc comp... more Marine observations offshore of Taiwan indicate intense deformation of the Luzon arc-forearc complex, with episodic eastward migration of the active deformation front across the complex. This active tectonic domain absorbs a significant amount of shortening between the Eurasia margin and the Philippine Sea Plate, which is moving towards N 310° E at about 8 cm/yr relative to Eurasia. Swath bathymetry and back-scattering data, together with seismic reflection and geopotential data obtained during the ACT (Active Collision in Taiwan) cruise onboard the R/V L'Atalante, showed major north to south changes in the tectonic style in both the indenting arc and the host margin. Structural observations show that the forearc basement of the Luzon arc no longer exists north of 22°30'N. To the south, only a small part of the forearc domain may remain beneath the Huatung Ridge (rear portion of the former Manila trench oceanic accretionary wedge including forearc and intra-arc sequences) and rear of the thrust wedge. A tectonic model involving the progressive underthrusting of large slices of the forearc basement may account for the contrasting styles of deformation encountered from south to north across the collisional orogen and apparent missing of the forearc region. The progressive subduction of the continental margin of China induces: 1) to the south, major eastward backthrusting and shortening of the forearc domain between the former oceanic accretionary wedge and the Luzon Arc volcanic edifice, 2) to the north, accretion of parts of the arc domain to the collisional belt associated with westward thrusting, eastward backthrusting at the base of the slope and block rotation.
The Philippine Sea Plate overrides the Eurasian Plate along the east-dipping Manila Trench betwee... more The Philippine Sea Plate overrides the Eurasian Plate along the east-dipping Manila Trench between Taiwan and Luzon islands. From south to north, the plate convergence gradually evolves from normal subduction of the South China Sea (SCS) lithosphere to initial collision of the Taiwan orogen. In order to better understand the deep crustal structures in this region, 11 multi-channel seismic reflection profiles were collected during R/V G. Langseth cruises MGL0905 and MGL0908 from April to July, 2009. The results show that large volume of sediments has accumulated in the northern Manila Trench and the oceanic crusts as thick as 10 km. Normal faults have widely distributed in the trench area due to the bending of subducting plate. The SCS basement generally deepens to the Luzon arc. Several seamounts intruded and extruded onto the volcanic SCS basement and lead to rough reliefs of the SCS basement. The rough-relief SCS basement has affected the deformation of decollement and sedimentary...