Overpressured Underthrust Sediment in the Nankai Trough Forearc Inferred From Transdimensional Inversion of High-Frequency Teleseismic Waveforms

Takeshi Akuhara, Takeshi Tsuji, Takashi Tonegawa

Research output: Contribution to journalArticlepeer-review

Abstract

Active-source seismic surveys have resolved the fine-scale P-wave velocity (Vp) of the subsurface structure in subduction forearcs. In contrast, the S-wave velocity (Vs) structure is poorly resolved despite its usefulness in understanding rock properties. This study estimates Vp and Vs structures of the Nankai Trough forearc, by applying transdimensional inversion to high-frequency teleseismic waveforms. As a result, a thin (∼1 km) low-velocity zone (LVZ) is evident at ∼6 km depth beneath the sea level, which is located ~3 km seaward from the outer ridge. Based on its high Vp/Vs ratio (∼2.5) and comparison to an existing seismic reflection profile, we conclude that this LVZ reflects a high pore pressure zone at the upper portion of the underthrust sediment. We infer that this overpressured underthrust sediment hosts slow earthquake activities and that accompanied strain release helps impede coseismic rupture propagation further updip.

Original languageEnglish
Article numbere2020GL088280
JournalGeophysical Research Letters
Volume47
Issue number15
DOIs
Publication statusPublished - Aug 16 2020

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

Fingerprint Dive into the research topics of 'Overpressured Underthrust Sediment in the Nankai Trough Forearc Inferred From Transdimensional Inversion of High-Frequency Teleseismic Waveforms'. Together they form a unique fingerprint.

Cite this