[S-GD02] 測地学・GGOS

[SGD02-P08] Postseismic effects of 2016 Elizovo M_w7.2 mid-focus earthquake

*Grigorii Viktorovich Nechaev^1,2、Nikolai Shestakov^1,2、Nikolai Titkov³、Hiroaki Takahashi⁴、Mako Ohzono⁵、Victor Pupatenko⁶、Evgenii Lialiushko² (1.Institute for Applied Mathematics FEB RAS, Vladivostok, Russia、2.Far Eastern Federal University, Vladivostok, Russia、3.Kamchatka branch of FRC Unified Geophysical Service RAS, Petropavlovsk-Kamchatskiy, Russia、4.Institute of Seismology and Volcanology, Hokkaido University, Sapporo, Japan、5.Earthquake Research Institute, University of Tokyo, Tokyo, Japan、6.Institute of Tectonics and Geophysics FEB RAS, Khabarovsk, Russia)

キーワード：earthquake modeling, postseismic displacements, mid-focus earthquake

Mid-focus earthquake M_w7.2 occurred 100 km to the north from Petropavlovsk-Kamchatskiy (the Kamchatka Peninsula, Russian Federation) on 30 January 2016 at the depth of 178 km. The earthquake generated the horizontal coseismic displacements up to ~ 5 mm and the appropriate surface subsidence and uplift ranging for -12 to +8 mm as far as a few hundred km from the epicenter. The Kamchatka permanent GNSS-network (Kam-Net) operated by Kamchatka Branch of Geophysical Survey of the Russian Academy of Sciences was used to detect coseismic crustal displacements invoked by the earthquake [Chebrov et al. 2016].
Some Kam-Net GNSS-stations located within ~ 200 km of seismic source demonstrated clear change of their secular movement velocity value and direction after the earthquake. The similar effect was previously reported and investigated by Shestakov et al., 2016 and Nechaev et al., 2021 for the 2013 M_w8.3 deep-focus Okhotsk earthquake occurred a few hundred km to the west from the Kamchatka Peninsula. We connect the observed GNSS-site velocities change to the postseismic effects of the 2016 Elizovo earthquake.
Coordinate time series of Kam-Net GNSS-sites were carefully processed and analyzed before and after the event. The impact of 2013 M_w8.3 deep-focus Okhotsk and shallow 2017 M_w7.8 Near Islands Aleutian earthquakes was taken into account. The different hypotheses including the temporal plate coupling change [Yuzariyadi & Heki 2021] and lithosphere-mantle viscoelastic relaxation were investigated and discussed. The late modeling was done by using VISCO1D and VISCO2.5D software [Pollitz, 2014].

References:
Chebrov V.N et al. Djupanovskoe earthquake 30.01.2016 K_S=15.7, M_w=7.2, I=6 (Kamchatka). Vestnik Krauntz 2016.1. P 5-16. (in Russian).
Nechaev G., Shestakov N., Takahashi H., Lialiushko E. Estimation of postseismic effects of 2013 Okhotsk sea M_w8.3 deep-focus earthquake. Abstracts of Japan Geoscience Union Meeting (JpGU 2021), SIT19-P04. Online May 31- June 6, 2021. http://www.jpgu.org/meeting_e2021/files/session_schedule_0324_e.pdf.
Pollitz, F. Post-earthquake relaxation using a spectral element method: 2.5-D case. Geophysical Journal International. 2014. 19 p.
Shestakov N., Nechaev G., Titkov N., Gerasimenko M., Bykov V., Pupatenko V., Serovetnikov S., Prytkov A., Vasilenko N., Sysoev D., Sorokin A., Takahashi H. and Ohzono M. Have the postseismic motions due to the May 24, 2013 M_w8.3 Okhotsk deep focus earthquake been discovered by the Russian far east GNSS networks? Abstracts of 9th Biennial Workshop on Japan - Kamchatka -Alaska Subduction Processes (JKASP 2016), May 31 - June 3, 2016, Fairbanks, USA. P. 65. Electronic resource: http://gps.alaska.edu/JKASP/JKASP2016_Scientific_Program_Abstracts.pdf
Yuzariyadi M., Heki K. Enhancement of interplate coupling in adjacent segments after recent megathrust earthquakes. Tectonophysics. 2021. 801 (228719). 30 p.

This work was supported by the RSF grant No. 22-27-00599.