Geomorphic features of surface ruptures associated with the 2016 Kumamoto earthquake in and around the downtown of Kumamoto City, and implications on triggered slip along active faults
Tóm tắt
The ~30-km-long surface ruptures associated with the M
w 7.0 (M
j 7.3) earthquake at 01:25 JST on April 16 in Kumamoto Prefecture appeared along the previously mapped ~100-km-long active fault called the Futagawa-Hinagu fault zone (FHFZ). The surface ruptures appeared to have extended further west out of the main FHFZ into the Kumamoto Plain. Although InSAR analysis by Geospatial Information Authority of Japan (GSI) indicated coseismic surface deformation in and around the downtown of Kumamoto City, the surface ruptures have not been clearly mapped in the central part of the Kumamoto Plain, and whether there are other active faults other than the Futagawa fault in the Kumamoto Plain remained unclear. We produced topographical stereo images (anaglyph) from 5-m-mesh digital elevation model of GSI, which was generated from light detection and ranging data. We interpreted them and identified that several SW-sloping river terraces formed after the deposition of the pyroclastic flow deposits related to the latest large eruption of the Aso caldera (86.8–87.3 ka) are cut and deformed by several NW-trending flexure scarps down to the southwest. These 5.4-km-long scarps that cut across downtown Kumamoto were identified for the first time, and we name them as the Suizenji fault zone. Surface deformation such as continuous cracks, tilts, and monoclinal folding associated with the main shock of the 2016 Kumamoto earthquake was observed in the field along the fault zone. The amount of vertical deformation (~0.1 m) along this fault associated with the 2016 Kumamoto earthquake was quite small compared to the empirically calculated coseismic slip (0.5 m) based on the fault length. We thus suggest that the slip on this fault zone was triggered by the Kumamoto earthquake, but the fault zone has potential to generate an earthquake with larger slip that poses a high seismic risk in downtown Kumamoto area.
Tài liệu tham khảo
Aoki K (2008) Revised age and distribution of ca. 87 ka Aso-4 tephra based on new evidence from the northwest Pacific Ocean. Quat Int 178:100–118
Committee for Compilation of the Geological Map of Kumamoto Prefecture (2008) 1: 100,000 geological map of Kumamoto Prefecture. Kumamoto Geotechnical Consultant Association Corp (in Japanese)
Fujiwara S, Yarai H, Kobayashi T, Morishita Y, Nakano T, Miyahara B, Nakai H, Miura Y, Ueshiba H, Kakiage Y, Une H (2016) Small-displacement linear surface ruptures of the 2016 Kumamoto earthquake sequence detected by ALOS-2 SAR interferometry. Earth Planets Space 68:160. doi:10.1186/s40623-016-0534-x
Geospatial Information Authority of Japan (2016a) Detection of crustal movement by ALOS-2 InSAR. http://www.gsi.go.jp/BOUSAI/H27-kumamoto-earthquake-index.html#3. Accessed 7 July 2016 (in Japanese)
Geospatial Information Authority of Japan (2016b) Provisional source fault model of the 2016 Kumamoto earthquake Accessed 7 September 2016. http://www.gsi.go.jp/common/000140781.pdf (in Japanese)
Goto H (2016) Extensive area map of topographic anaglyphs covering inland and seafloor from detailed digital elevation model for identifying broad tectonic deformation. In: Kamae K (ed) Earthquakes, Tsunamis and nuclear risks: prediction and assessment beyond the Fukushima accident. Springer, Japan, pp 65–74. http://link.springer.com/chapter/10.1007%2F978-4-431-55822-4_5
Goto H, Sugito N (2012) Fault geomorphology interpreted using stereoscopic images; produced from digital elevation models. E-J GEO 7:197–213 (in Japanese with abstract in English)
Ikeda Y, Chida N, Nakata T, Kaneda H, Tajikara M, Takazawa S (2001) 1:25,000-scale active fault map in urban area “Kumamoto”. Technical report of the Geographical Survey Institute, Ibaraki, D1-No. 388 (in Japanese)
Ishizaka S, Watanabe K, Takada H (1992) Subsidence rate of the underground quaternary system for the past 150,000 years in the Kumamoto Plain, Kyushu, Japan. Quat Res 31:91–99 (in Japanese with abstract in English)
Japan Meteorological Agency (2016) CMT solutions of the earthquake occurred in April, 2016. http://www.data.jma.go.jp/svd/eqev/data/mech/cmt/cmt201604.html. Accessed 7 July 2016 (in Japanese)
King GCP, Stein RS, Lin J (1994) Static stress changes and the triggering of earthquakes. Bull Seismol Soc Am 84:935–953
Kumahara Y, Goto H, Nakata T, Ishiguro S, Ishimura D, Ishiyama T, Okada S, Kagohara K, Kashihara S, Kaneda H, Sugito N, Suzuki Y, Takenami D, Tanaka K, Tanaka T, Tsutsumi H, Toda S, Hirouchi D, Matsuta N, Moriki H, Yoshida H, Watanabe M (2016) Distribution of surface rupture associated with the 2016 Kumamoto earthquake and its significance. Japan Geoscience Union Meeting 2016, MIS34-05
Kumamoto City Waterworks Bureau (1980) The underground water in and around Kumamoto city. Kumamoto City Waterworks Bureau (in Japanese)
Matsuda T (1975) Magnitude and recurrence interval of earthquakes from a fault. J Seismol Soc Jpn 28:269–283 (in Japanese with abstract in English)
Matsumoto N, Yoshihiro H, Sawada A (2016) Continuity, segmentation and faulting type of active fault zones of the 2016 Kumamoto earthquake inferred from analyses of a gravity gradient tensor. Earth Planets Space 68:167. doi:10.1186/s40623-016-0541-y
Murayama M, Matsumoto E, Nakamura T, Okamura M, Yasuda H, Taira A (1993) Reexamination of the eruption age of Aira-Tn (AT) obtained from a piston core off Shikoku; determined by AMS 14C dating of planktonic foraminifera. J Geol Soc Jpn 99:787–798 (in Japanese with abstract in English)
Nakata T, Imaizumi T (eds) (2002) Digital active fault map of Japan. University of Tokyo Press, Tokyo (in Japanese with abstract in English)
National Research Institute for Earth Science and Disaster Resilience (2016) Earthquake mechanism information by broadband seismic network (F-net). http://www.fnet.bosai.go.jp/event/joho.php?LANG=en
Nishimura T, Tobita M, Yarai H, Amagai T, Fujiwara M, Une H, Koarai M (2008) Episodic growth of fault-related fold in northern Japan observed by SAR interferometry. Geophys Res Lett. doi:10.1029/2008GL034337
Okada Y (1992) Internal deformation due to shear and tensile faults in a half-space. Bull Seismol Soc Am 82:1018–1040
Research Group for Active Faults of Japan (1991) Active faults in Japan: sheet maps and inventories, revised edn. University of Tokyo Press, Tokyo (in Japanese with abstract in English)
Research Group for Active Tectonics in Kyushu (1989) Active Tectonics in Kyushu. University of Tokyo Press, Tokyo (in Japanese with abstract in English)
Watanabe K, Momikura K, Tsuruta K (1979) Active faults and parasitic eruption centers on the west flank of Aso caldera, Japan. Quat Res 18:89–101 (in Japanese with abstract in English)
Watanabe K, Takada H, Okabe R, Nishida A (1995) Stratigraphic relation between fluvial terrace deposits and widespread tephra beds in the middle reaches of the Sirakawa, Kumamoto Prefecture, Japan. Memoirs of the Faculty of Education. Kumamoto University. Nat Sci 44:15–22 (in Japanese with abstract in English)
Wei M, Sandwell D, Fialko Y, Bilham R (2011) Slip on faults in the Imperial Valley triggered by the 4 April 2010 Mw 7.2 El Mayor–Cucapah earthquake revealed by InSAR. Geophys Res Lett. doi:10.1029/2010GL045235