RING-SHAPED SEISMICITY STRUCTURES,
BEING FORMED PRIOR TO LARGE AND GREAT EARTHQUAKES IN THE WEST AND EAST OF THE PACIFIC OCEAN

Yu.F. Kopnichev1, I.N. Sokolova2 

1 Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia

2 Institute of Geophysical Research of Ministry of Energy of Republic Kazakhstan, Almaty, Kazakhstan

Abstract. We have been considering seismicity characteristics prior to large and great earthquakes at the periphery of Pacific. It was established that before events of Мw = 7.0–9.2, occurred in 1964–2016, ring-shaped seismicity structures have been formed, as a rule, in two depth ranges: 0–33 and
34–70 km. We obtained correlation dependences of «shallow» (L) and «deep» (l) seismicity rings sizes, threshold magnitude values (Mt1 and Mt2 respectively), and also their formation duration (Т1 и Т2) on magnitudes Mw of main events. It was shown that ring structures sizes (for the given Mw) are essentially less for earthquakes at the west of Pacific than at the east of it. At the same time parameters Mt1 and Mt2 are similar for two regions considered. Parameters Т1 and Т2 vary essentially for different events, in the middle they equal ~27–30 years. It is supposed that ring-shaped structures formation is connected with deep-seated fluid migration, and their characteristic differences for the western and eastern outskirts of Pacific are connected with different fluid content within the earth crust and uppermost mantle of the regions considered. This conclusion agrees with data on aftershock processes peculiarities for large earthquakes at the west and east of Pacific.

Keywords: seismicity, ring-shaped structures, large earthquakes, deep-seated fluids.

About the authors

KOPNICHEV Yuri F. – Ph. D. (phys. and math.), professor, chief researcher, Schmidt Institute of Physics of the Earth, Russian Academy of Sciences. Moscow, Russia. Tel.: +7 (7272) 956-350. E-mail: yufk777@mail.ru

SOKOLOVA Inna N. – Ph. D. (phys. and math.), senior researcher, Institute of Geophysical Research of Ministry of Energy of Republic Kazakhstan. Almaty, Kazakhstan. Tel.: +7 (7272) 631-330.
E-mail: sokolova.inessa@mail.ru