June 27, 1957 Earthquake: Chita, Russia

June 27, 1957, 00:09:30 UTC, 56.2 N, 116.4 E, depth 15 km, magnitude 7.6, intensity X. The epicentral zone of the earthquake is in the Namarakit embrionic trough of the Baikal type. During

the onset of the earthquake, the trough subsided a minimum of 5-6 m and shifted westward, and the adjacent part of the Udokan Range raised 1-1.5 m and shifted eastward 1-1.2 m. As a result, a complex system of seismic dislocations arose having an overall extent of about 30 km. Fault and upthrust shears were dominant among the seismic dislocations, but tensile fissures (up to 7-8 m. and in one instance up to 19 m) also were found. There also was evidence of compression fissures up to 3.8 m in height. Furthemore, twisted folds,

seismic-domed structures, shear fissures, etc., were found.

The epicentral zone of the earthquake was in an

unpopulated area. R. A. Kurushin [l] found three labases

here (a labase is a massive cut surface. mounted

on sawed-off tree trunks). Two of them--500 m from the

seismic-dislocation line and 13 km from the eastern

flank of this line on the northern slope of the Namarakit

massif--had been thrown from poles and destroyed;

the third--13 km to the northeast from the western

flank of the system--was undamaged.

The earthquake's intensity at the epicenter is

estimated from macroseismic data at 9-10; from geomorphological data it is rated 10-11. On the average

the intensity is 10.

Many stoves and most chimneys were destroyed in

the nearest populated areas--in the Kedrovyy mines (50

km west of the center of the epicentral zone) and in

Bezymyannyy. Part of a chimney was ruined in the village

of Mnogoobeshchayashchaya Kosa (about 30 km west

of the epicenter). The whole area adjacent to the epicenter

is marked by an unequal distribution of macroseismic

effects [V-16]. In the city of Bodaybo (250 km from the epicenter) the cracking of stacks, partial ruin of stoves, and, in some homes, the falling of plaster were noted. Cracks appeared in buildings, and plaster crumbled in the city of Chita (490 km from the epicenter).

The overall felt area exceeds 2 million km2. The magnitude of the earthquake was redefined using the

data of seven seismic stations. Estimates from the

macroseismic data (MMacro=7.6) and the parameters of the seismic dislocations agree with the instrumental magnitude.

(above from reference #223)

June 27, 1957, 00:09:28, 56.5 N, 116 E, northeast of Lake Baikal, U.S.S.R., magnitude 7.9, damage at Chita. (reference #45)

June 27, 1957, 00:09:28, 56.5 N, 116 E, magnitude 7.9. (reference #88)

1957, Outer Mongolia, 1200 deaths. (reference #1133)