JpGU-AGU Joint Meeting 2020

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-SS Seismology

[S-SS15] Fault Rheology and Earthquake Physics

convener:Keisuke Yoshida(Tohoku University), Keishi Okazaki(Japan Agency for Marine-Earth Science and Technology), Shunya Kaneki(Disaster Prevention Research Institute, Kyoto University), Hiroyuki Noda(Kyoto University, Disaster Prevention Research Institute)

[SSS15-P38] Foreshocks immediately before the starting of earthquakes

*Masaki Yamana1, Aitaro Kato1 (1.Earthquake Research Institute, the University of Tokyo)

There are many studies describing foreshock activities to understand
earthquake initiation process.
On the other hand, few researches remarks on activity immediately
before the starting of earthquakes.
For example, Tape et al. (2018) shows simultaneous activity of small
earthquakes and very-low-frequency event (VLFE) within 20 seconds
before Mw3.7 earthquake in Alaska and discuss the relationship between
these events and nucleation process.

In this research, we have visually inspected waveform of shallow
crustal earthquakes from 2003 to 2019 with magnitude greater than 3.5
(depth < 15km), in Japan.
From this exploration, we find out that foreshocks occurred
immediately before some mainshocks within about 30 seconds.
After detection, we plan to precisely relocate the foreshock and
mainshock events applying a double-differential algorithm and discuss
the relationship between them.