RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 10, ES5003, doi:10.2205/2007ES000268, 2008
[15] The total epicenter area of both earthquakes represents the rectangle of northeastward extension as described above. It is mainly associated with riverheads of the Vyvenki River right tributaries within the Navkyrvayam and Ogiranvayam nappes of the Vyvenki uplift. The area is bounded on the north by the Vyvenki-Vatyn deep fault in its length between the Vetrovayam and Levtyrinvayam (Latyrinavayam) Rivers and the thrust faults that extend it northeastwards. On the southeast the uplift is bounded by the Vyvenki deep fault covered with soft deposits of the Vyvenki River valley [Kravchenko et al. 2000]. The central longitudinal axis of the common epicenter area is associated with that of the Vyvenki riftogenic depression manifested on the surface as the Vyvenki River valley. The southern half of the common epicenter area coincides with the Khailino graben filled with the Miocene coal-bearing molasse that begins at the Tapelvayam River mouth (right tributary of the Vyvenki River) on the southwest and extends to the Inibuvayam River (left tributary of the Tylgovayam River) on the southeast. The graben is bounded on the southeast by the fault of the Tapelvayam River of northwestward direction that is traced southeastward to the Govena Peninsula for the length of the Panetivayam River. The southern part of the Khailino graben is represented by marine molasse and is framed by riftogenic structures of the Tylgovayam depression [Kravchenko and Razumnyi, 2002].
[16] The Khailino earthquake happened 10 km east of the Khailino Village. It was preceded by 4 foreshocks and accompanied by 62 aftershocks. One and a half month after the main shock, the southwestward aftershocks associated with the southwestern wedge-out of the Tylgovayam riftogenic depression, increased. Different estimates of the focal depth [Lander et al., 1991] range from 13 to 35-50 km, indicating likely crustal or transcrustal foci.
[17] The common swarm, i.e. the Khailino and Olyutorka earthquakes rectangle measures 182
6-8 km.
It completely fits in with outlines of depressions recognized in the Vyvenki River valley
according to MTZ records
[Moroz, 1987].
The depression of the basement top along the 10-km isohypse is
approximately superposed onto area between the Vetvei River mouth, Mt. Maini-Nayuyu, and the
Nayuyu-Gytkhym Lake. It is just at the northern boundary of the basement 10-km isopach that the
Vyvenki River channel discordantly changes its direction from southwestern to southeastern over a
length of about 10 km and then again turns southwestward. The comparison of the earthquake
clusters with the geologic map shows that northeastern boundaries of the areas are defined by
transverse northwestern disturbances underlined by the channels of low reaches of the rivers
Vetrovayam, Tapelvayam, Khatapvayam (extending at 85 km northwestward to the Unnaivayam
River channel), Atalavayam (extending at 45 km northwestward to the Ev'einvayam River channel),
and by the southeastward extension of the Enychavayam River channel. These disturbances are
recorded in the Koryak flyschoid zone extending at 32-55 km northwestward (310o) from the
boundary of the common swarm.
[18] The maximum depth of the Upper Cretaceous basement reaches 3 km and the 3-km isopach is associated with the Khailino earthquake area.
Citation: 2008), Tectonic position of the Khailino and Olyutorka earthquakes, Russ. J. Earth Sci., 10, ES5003, doi:10.2205/2007ES000268.
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