[S-CG45] Science of slow-to-fast earthquakes

[SCG45-P32] Further Investigation on Strongly Scattering Medium Along Slow-earthquake Fault Zones based on Observations of Short-duration Tremors

*Akiko Toh¹, Yann Capdeville², Wu-Cheng Chi³, Satoshi Ide¹ (1.Department of Earth and Planetary Science, University of Tokyo, 2.Laboratoire de Planétologie et de Géodynamique, Université de Nantes, 3.Institute of Earth Sciences, Academia Sinica)

Keywords:Non-volcanic tremor, Nankai trough, slow earthquake

Tremors are a type of slow-earthquake with long-duration signals compared to ordinary earthquakes. The long signals have been considered to solely reflect their long source-time process. Here, we report on evidence showing that the source processes of tremors are not always long. We refer to such observations as short-duration tremors. They were recorded by ocean-bottom seismometers placed very close to the source. They exhibit a short-duration signal when recorded near the source but exhibit a typical long-duration signal elsewhere. We show through numerical simulations that their features can be captured by considering a strongly scattering medium around their source. One such anomalous structure can be small low-velocity inclusions distributed around the seismic source. The inclusions could be seismic expressions of the geologically detected aquifers in a tremor source region. Furthermore, this structure could be embedded along the slow-earthquake fault zone and play a crucial role in their source process.
In the presentation, we will focus on the following three points and proceed with the discussion.
(1) Short-duration tremors are end-member of tremors, although their waveforms resemble those of ordinary earthquakes at some stations.
(2) Sensitivity of some parameters of the proposed distributed-inclusion model.
(3) Definition of short-duration tremors in comparison with low frequency earthquakes.