OKHOTSK-III EARTHQUAKE 24.05.2013 with Mwreg=8.3, I0=6 (Sea of Okhotsk)

Abstract

The strongest deep earthquake on May 24, 2013 (Mwreg=8.3) is discussed. It occurred under the Sea of Okhotsk at a depth of about 630 km. The instrumental hypocenter location reported by the KB GS RAS is φ=54.75N, λ=153.78E, h=630 km. Three magnitudes were obtained: local magnitude ML=7.8, code-wave magnitude Mc=7.6, moment magnitude Mwreg=8.3. The Okhotsk earthquake hypocenter is located on the northern part of the ancient slab, practically at the lower end of the seismogenic region. The earthquake caused significant co-seismic displacements at most GNSS observation points. The earthquake focal mecha-nisms solutions have been obtained by three ways. The solutions are very similar. The submeridial hollow falling nodal plane seems more preferable. For the deep quake of May 24, 2013, a series of aftershocks were registered. The aftershock process had three consistent stages with different decay character. The cloud of deep-focus aftershocks has the 400200 km size, with the 450–700 km depth range and is extended in the North–South direction. The aftershock process has the three-phase character and can be considered as a stream of seismic events decreasing in time with three successive stages with different attenuation modes. The change in attenuation modes is associated with strong aftershocks. The duration of the decaying after-shock process is ~ 280 days. The anomalous distribution of impact was observed for the earthquake: 1) a large range of macroseismic effect – quake was felt throughout the World; 2) in the territory of Kamchatka, maximum shakes and ground motions were observed at the points located on the eastern coast of Kamchat-ka, and at comparable northern and western distances macroseismic and instrumental intensities were lower. Despite the globality of the macroseismic effect, in the nearest settlements (Kamchatka region), the earth-quake was felt with intensity up to 5–6 and caused no damage. The May 24, 2013 earthquake produced many strong motion records. The ground motion characteristics such as peak amplitudes of motion, spectral shape and response spectrum were received using the records of the earthquake from Kamchatka network of digital accelerographs.