Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-SS Seismology

[S-SS10] Seismicity

Tue. May 28, 2019 10:45 AM - 12:15 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Kei Katsumata(Institute of Seismology and Volcanology, Hokkaido University)

[SSS10-P09] Time series analyses of the seismic activities in southwestern Japanese Island to southeastern Korean Peninsula excited by the deep fluid heat flow

*Takayuki Kawabe1 (1.Faculty of Education, Arts and Sciences, Yamagata University)

Keywords:time series analyses of seismic activities, deep fluid heat flow, southwestern Japanese Island

More than eight series of large damaging earthquakes occurred since November 2015 in southwestern Japanese Islands. They are as follows;
1) 2015/11/15 earthquakes of Northwestern margin of Okinawa Trough N31.33050°, E128.71733°, Depth: 9.4km, M5.9.
Foreshock: M5.1 (11/14), largest aftershock: M5.5 (2016/05/07).
2) 2016/04/16 2016 Kumamoto Earthquakes N32.75450° E130.76300°, Depth: 12.45km, M7.3.
Foreshock: M6.5 (04/14), M6.4 (04/15), largesrt aftershock: (04/16) M5.9.
3) 2016/09/12 earthquake of Southeastern Korean Peninsula N35.79817° E129.27167°, Depth: 36.0km, M5.8.
Foreshock: M5.2 (40 minutes before), Largest aftershock: M5.2 (2017/11/15).

4) 2016/10/21 earthquake of Central Tottori in 2016 N35.38050° E133.85617°, Depth: 10.61km, M6.6.
Foreshocks: low frequency earthquakes, aftershocks: containing low frequency earthquakes.
5) 2017/11/15 earthquake of Southeastern Korean Peninsula N36.19584° E129.39417°, Depth: 11.0km, M5.6.
6) 2018/02/11 earthquake of Southeastern Korean Peninsula N36.09883° E129.45700°, Depth: 4.0km, M4.6.
7) 2018/04/09 earthquake of Western Shimane Prefecture in 2018 N35.18467° E132.58667°, Depth: 12.13km, M6.1.
8) 2018/06/18 Northern Osaka Earthquake in 2018 N34.84433° E135.62167°, Depth: 12.98km, M6.1.

Positions of the formar four eathquakes and the later four earthquakes shift from the west to the east.
The number and scale of the earthquakes of Northwestern margin of Ryukyu Trough is reduced just several days berore the 2016 Kumamoto Earthquakes, and the number and scale of them is just restored after the 2016 Kumamoto Earthquakes. This seems to have a strong relationship between the earthquakes of Northwestern margin of Okinawa Trough and the 2016 Kumamoto Earthquakes. This suggests that such two strongly related earthquakes may be drived by the migration of thermal enargy because the earthquake activities are restored.
Seismic activity contined more than two years in the case of the earthquakes of Southeastern Korean Peninsula and large eathquakes often recured there. Their hypocenters show remarkable distribution. That is to say, they distribute not along any plane but along three dimensionally bent lines. on the lines, earthquakes occurred from the bellow to the upper in the lower to the upper crust. This means that the earthquakes of southeastern Korean Peninsula occurred not in an elastomechanical system but other system as thermal energy. Next earthquakes, just after the earthquakes of southeastern Korean Peninsula, occuring in the central Tottori in 2016 contains large number of low frequency earthquakes through the foreshocks to the aftershocks. The main shock of the ceentral Tottori in 2016 is actually drived by the thermal liquid enargy.
According to such evidences of the liquid flow causing the earthquakes, the large earthquakes occuring in the upper crust of Southwest Japan would be driven by the eastward transmigrating thermal energy in the upper mantle (Tsunoda et al., 2013).

Tsunoda, F., Choi, D.R. and Kawabe, T., 2013. Thermal energy transmigration and fluctuation. NCGT Journal, v.1, p.65-80.