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Lack of observation network in the vicinity of oceanic intraplate earthquake lead the estimation of coseismic fault slip with high uncertainty. Satriano et al. [2] and Wei et al. [3] found NNE trending left-lateral slip as the primary features. In another hand, Yue et al. [4] and Hill et al. [5] proposed WNW trending right-lateral faults structure as the main characteristic. Here, we investigate the coseismic fault model that could explain the coseismic offset both vertical and horizontal in a 3-D heterogeneous earth structure. We constructed finite element model that include three-dimensional velocity structure, topography/bathymetry, spherical-earth and subducting slab. In this study, we employed scaling slip to adjust slip amount and total seismic moment. Instead of original slip amount, we preserve seismic moment as a basis comparison. Based on vertical and horizontal observation data, WNW trending right-lateral fault could fit better than NNE trending left-lateral fault. The present study demonstrates best-fit calculation using scaling slip optimized to the horizontal or vertical observation lead the both fault model worsen the misfit of vertical or horizontal component, respectively. This result analysis indicates a trade-off between vertical and horizontal component and reflects the importance of revisiting the fault slip modeling incorporating vertical and horizontal data equally.Lack of observation network in the vicinity of oceanic intraplate earthquake lead the estimation of coseismic fault slip with high uncertainty. Satriano et al. [2] and Wei et al. [3] found NNE trending left-lateral slip as the primary features. In another hand, Yue et al. [4] and Hill et al. [5] proposed WNW trending right-lateral faults structure as the main characteristic. Here, we investigate the coseismic fault model that could explain the coseismic offset both vertical and horizontal in a 3-D heterogeneous earth structure. We constructed finite element model that include three-dimensional velocity structure, topography/bathymetry, spherical-earth and subducting slab. In this study, we employed scaling slip to adjust slip amount and total seismic moment. Instead of original slip amount, we preserve seismic moment as a basis comparison. Based on vertical and horizontal observation data, WNW trending right-lateral fault could fit better than NNE trending left-lateral fault. The present study demonstrate...

We developed a centroid moment tensor (CMT) catalogue of earthquakes in and around Indonesia (InaCMT) using data from the nationwide broadband seismograph network in Indonesia. We obtained CMT solutions for about 500 earthquakes that occurred in and around Indonesia between 2006 and 2009. The moment magnitudes ranged from 4.5 to 8.3. We examined the accuracy of the CMT solutions of the InaCMT catalogue by comparing them with those obtained by the Global CMT (GCMT) Project. The seismic moments and focal mechanisms of these catalogues were highly consistent with each other, but we found systematic differences between the catalogues in the source centroid locations of earthquakes off Sumatra. The InaCMT source centroid locations were closer to the hypocenter locations in the Preliminary Determination of Earthquakes (PDE) of the U.S. Geological Survey compared to those of GCMT. The systematic deviations in the GCMT source centroid locations may mainly reflect insufficient azimuthal coverage of the stations used for the inversions as well as uncertainties in the Earth model. Using the InaCMT catalogue, we investigated seismic activity related to the off Bengkulu seismic sequence on 12 September 2007 (Mw = 8.3, 7.9, and 6.8), southwest of Sumatra, and the earthquakes northwest of the island of New Guinea on 3 January 2009 (Mw = 7.7 and 7.4). In the aftershock activity of the 2007 off Bengkulu seismic sequence, we found that shallow earthquakes were aligned along the eastern coast of Siberut Island, located between the Sunda trench and Sumatra. These earthquakes may have occurred along the Mentawai fault or another unknown fault. The focal mechanisms of the earthquakes were dominantly reverse slip, although the Mentawai fault has been considered to be a strike-slip fault. Shallow large earthquakes along this fault may cause damage above the source region and generate large tsunamis. We found that the 2009 earthquakes northwest of New Guinea occurred along the Manokwari trough and that the aftershocks were aligned along a plane dipping about 30° to the south, indicating that the Pacific and/or Philippine Sea plate subducts below the Australian plate at the Manokwari trough. The InaCMT catalogue enables us to perform detailed analyses of seismic activity in and around Indonesia, which contributes to better understanding of tectonic features and potential seismic and tsunami hazards in Indonesia as well as the coastal regions of the Pacific and Indian Oceans.

We have conducted geodetic and geomorphic observations in the northernmost part of Sumatra, Indonesia to monitor strain accumulation in the vicinity of the northern Sumatran fault. Evaluation of the earthquake generation potential in this region is highly urgent because of a large fault slip rate, absence of major earthquakes for more than 100 years and recent Coulomb stress increase on the fault due to the 2004 Sumatra-Andaman earthquake (M w 9. 2). We have deployed Aceh GPS Network for the Sumatran Fault System (AGNeSS) since 2005. The data collected have been used for estimating slip/locking distribution of the Sumatran fault and constructing a comprehensive model for postseismic deformation after the 2004 event. Tectonic geomorphic features are also important to reveal long-term slip history of the fault. We have used high-resolution stereo-paired ALOS (Advanced Land Observing Satellite) PRISM (Panchromatic Remote-sensing Instrument for Stereo Mapping) satellite images to map the surface trace of the Sumatran fault and conducted field observations to ensure the trace by geomorphic and geologic evidence. We introduce preliminary results of the fault mapping together with a brief description of the crustal deformation field detected by GPS.

[1] The Kuril arc collides with the northeast Japan arc in the southern part of Hokkaido, Japan. 3-D tomographic inversion of data from a dense network of sensitive ocean-bottom seismographs and land stations has allowed imaging of previously unseen details of the arc-arc collision structure. A low velocity body dips gently southwestward, at depths of 35 to 45 km, from east of the Hidaka Mountains to the source area of the 1982 Urakawa-oki destructive earthquake (Ms 6.8). The low velocity body is the lower half of the lower crust of the Kuril arc, which must have been delaminated by the collision. We believe that the continuing collision of the delaminated lower crust with the northeast Japan arc resulted as an episode of aseismic slow slip prior to the 1982 Urakawa-oki earthquake as well being the reason for the high seismic activity in this region.