Japan Geoscience Union Meeting 2016

Presentation information

International Session (Poster)

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

[S-CG20] Intermediate-depth and deep earthquakes: their origins and material properties of subducting slabs

Tue. May 24, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Keiko Kuge(Department of Geophysics, Graduate School of Science, Kyoto University), Saeko Kita(National Research Institute for Earth Science and Disaster Prevention), Alexandre Schubnel(CNRS), Geoffrey Abers(Cornell University, Department of Earth and Atmospheric Sciences, New York, USA)

5:15 PM - 6:30 PM

[SCG20-P06] The 30 May 2015 Bonin Deep Earthquake and the 660-km Discontinuity around its Source Region

*Keiko Kuge1 (1.Department of Geophysics, Graduate School of Science, Kyoto University)

We model P and SH waveforms at regional and teleseismic distances from the 30 May 2015 Bonin deep earthquake (depth 664km, Mw7.8; USGS), investigating the rupture propagation and the depth of the 660-km discontinuity. The results suggest that seismic waves from a 660-km discontinuity below the source region cannot be needed. A significant, subhorizontal 660-km discontinuity could not be located below the source region. Seismic waves from the Bonin earthquake were recorded by a number of broadband stations in a wide range of distance around the world, which include many Japanese stations at regional distances. Along with data collected by IRIS DMC, we use data recorded by F-net in Japan. Because high-frequency waves, which could be associated with the descending Pacific slab, were observed in eastern Japan, we use F-net data only from western Japan. The P and SH waves in western Japan have an apparently long duration, consisting of pulses. Because the distance of the stations ranges from 7 to 16 degrees, the 660-km discontinuity may affect the waveforms, depending on its depth. Changing the depth in the velocity model iasp91, we perform waveform inversion for spatiotemporal distribution of moment release on a plane, based on the method of Kuge (2003, 2010). Results from P waves show that the waveform fit becomes worse when the 660km-discontinuity is assumed below the source region. This is consistent with the observation of a simple pulse for P and SH waves from an aftershock.