โ Scribed by V. M. Zobin; E. I. Gordeev; V. F. Bakhtiarov; E. I. Ivanova; Yu. M. Khatkevich; V. N. Khodenko; V. E. Levin; V. P. Mityakin
No coin nor oath required. For personal study only.
The earthquake of 6 October 1987 (M = 6.6), which occurred near the Shipunsky Cape, Kamchatka, was the largest crustal event in the vicinity of the main city of Kamchatka -Petropavlovsk-Kamchatsky -during the last three decades. It was followed by numerous aftershocks. This earthquake allowed us to test the effectiveness of the seismic hazard monitoring in Kamchatka, including the seismological, geodetic and hydrogeochemical surveys. The seismic survey provided the location and source nature of the main shock and aftershocks and the seismic environment of the main shock. The geodetic and hydrogeochemical surveys have yielded data on the response to earthquakes of the Earth's surface deformations, water level, and chemical elements concentration in the underground water.
As a result, the following data were obtained:
-The earthquake of 6 October had a seismic moment 4-10 El8 Nm, thrust type of faulting and the source volume of 20 x 20 ร 10 km 3. The maximum intensity was VI-VII (MSK-64 scale) and maximum acceleration 88 cm/s 2. -Before this event, a relative increase in the number of the upper mantle (depth more than 100 km) moderate magnitude earthquakes during 5 years and a one-year period of seismic quiescence for small shallow earthquakes, were recognized. Significant anomalies in HCO 3 and H3BO3 concentrations in the underground waters were observed in the wells a week before the main shock.
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