Waveform inversion for slip distribution of the 2006 Java tsunami earthquake by using 2.5D finite-difference Green’s function

Abstract

We first incorporate the large effect of near-source heterogeneity on teleseismic body waveforms in the inversion of the slip distribution of the 2006 Java tsunami earthquake. We incorporate the effect by computing the response of an assumed "2.5D" model structure of the Java trench by a 2.5D finite-difference method. Based on a simulation of inversion, we suggest that intense smearing is possible when we apply 1D Green's functions in the analysis, and that it may obscure the slip pattern. In the inversion of real data, we confirm macroscopic features, such as a long duration (∼165 s) and a slow rupture velocity (∼1.25 km/s). The region of the initial rupture is found to be isolated from the eastern broad region in which we further identify a heterogeneous slip distribution. Most of these regions are likely to be at the sedimentary plate interface where the accreted sediment and the subducting plate are in contact. In particular, the nearly "isolated" feature of a shallow slip region suggests a possible faulting in the shallowest part of the sedimentary plate interface without being strongly enforced by the rupture propagated from the deeper part of the fault. Such heterogeneity suggests a highly variable frictional behavior at the sedimentary plate interface.

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“…4. Deconvolve the mainshock using the empirical Green's function event and a nonnegative inversion method (after Okamoto and Takenaka, 2009). …”

Introduction of uncertainty of Green's function into waveform inversion for seismic source processes

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Coherent Seismic Arrivals in the P Wave Coda of the 2012 Mw 7.2 Sumatra Earthquake: Water Reverberations or an Early Aftershock?

“…The 2‐D synthetics presented by Yue et al () suggest that such scattering may occur, but as discussed in their paper, 3‐D modeling with realistic bathymetry and real station distributions should be performed to better resolve this issue. Okamoto and Takenaka () highlighted that 2.5‐D/3‐D modeling with realistic bathymetry is necessary to unravel the complex P and SH waves. Most previously reported cases of water reverberations have been for reverse‐ or normal‐faulting earthquakes (An et al, ; Chu et al, ; Okamoto & Miyatake, ; Okamoto & Takenaka, ; Wiens, ), and is unclear whether strike‐slip earthquakes like the 2012 M w 7.2 mainshock are efficient at generating water reverberations.…”

“…Okamoto and Takenaka () highlighted that 2.5‐D/3‐D modeling with realistic bathymetry is necessary to unravel the complex P and SH waves. Most previously reported cases of water reverberations have been for reverse‐ or normal‐faulting earthquakes (An et al, ; Chu et al, ; Okamoto & Miyatake, ; Okamoto & Takenaka, ; Wiens, ), and is unclear whether strike‐slip earthquakes like the 2012 M w 7.2 mainshock are efficient at generating water reverberations. Furthermore, the 2012 mainshock and its seaward EGFs are deeper than 20 km (International Seismological Centre, ), in contrast to the shallower depths of previously reported earthquakes that effectively excited water phases (≤15 km; An et al, ; Chu et al, ; Okamoto & Miyatake, ; Wiens, ).…”