Japan Geoscience Union Meeting 2016

Presentation information


Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG63] Dynamics in mobile belts

Tue. May 24, 2016 9:00 AM - 10:30 AM A08 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Norio Shigematsu(Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology), Aitaro Kato(Graduate School of Environmental Studies, Nagoya University), Hikaru Iwamori(Geochemical Evolution Research Program, Japan Agency for Marine-Earth Science and Technology), Yasutaka Ikeda(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Chair:Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Bunichiro Shibazaki(International Institute of Seismology and Earthquake Engineering, Building Research Institute)

9:15 AM - 9:30 AM

[SCG63-26] Deformation rates of island-arc crust estimated from seismic, geodetic, and geomorphic data

*Mitsuhiro Matsu'ura1, Akemi Noda2, Yukitoshi Fukahata3 (1.The Institute of Statistical Mathematics, 2.Kozo Keikaku Engineering Inc., 3.Disaster Prevention Research Institute, Kyoto University)

Keywords:island arc, deformation rate, inelastic strain, seismic data, geodetic data, geomorphic data

Steady plate subduction brings about steady uplift of the island-arc lithosphere [1]. This process is simply explained as convex upward bending of an elastic plate by the effect of gravity [2]. So, there is no analogy in mechanism between the steady uplift and steady horizontal shortening or stretching of island-arc crust. The island-arc crust is basically elastic, but it includes a number of defects. Brittle fracture and/or plastic flow at these defects, which occur so as to release the overall elastic strain energy produced by mechanical interaction at plate interfaces, cause the horizontal shortening or stretching of island-arc crust [3]. To sum up, the crustal shortening or stretching is a purely inelastic deformation process. In northeast Japan, for example, the evidence of crustal shortening has been reported from seismic, geodetic, and geomorphic data [4, 5]. The point is a discrepancy in its rates. One of the reasons is difference in the length of observation periods. Actually, geodetic observation is too short to cover the entire cycle of large earthquakes. Another, more essential, reason is that different kinds of data provide different information about crustal deformation; that is, seismic and geomorphic data provide information about purely inelastic crustal deformation, whereas geodetic data provide information about total (elastic + inelastic) crustal deformation. So, we cannot directly compare the crustal shortening rates from geodetic data with those from seismic and geomorphic data unless geodetically observed deformation is divided into the elastic and inelastic parts [3].

[1] Matsu’ura, M. and T. Sato (1989), A dislocation model for the earthquake cycle at convergent plate boundaries, Geophys. J. Int., 96, 23-32.
[2] Fukahata, Y. and M. Matsu’ura (2016), Characteristics of island arc deformation due to steady plate subduction, Geophys. J. Int., 204, 825-840.
[3] Noda, A. and M. Matsu’ura (2010), Physics-based GPS data inversion to estimate 3-D elastic and inelastic strain fields, Geophys. J. Int., 182, 513-530.
[4] Wesnousky, S.G., C.H. Scholz, and K. Shimazaki (1982), Deformation of island arc: Rates of moment release and crustal shortening in intraplate Japan determined from seismicity and Quaternary fault data, J. Geophys. Res., 87, 6829-6852.
[5] Ikeda, Y., S. Okada, and M. Tajikara (2012), Long-term strain buildup in the Northeast Japan arc-trench system and its implications for gigantic strain-release events, J. Geol. Soc. Jpn., 118, 294-312.