December 4, 1957 Earthquake: Mongolia

December 4, 1957, 03:37:45 UTC, 45.5 N, 99.5 E, shallow depth, magnitude 8.3 MS. (reference #88)

December 4, 1957, Mongolia, magnitude 8.3 MS, 8.1 Mw. (reference #1314)

December 4, 1957, Mongolai: Altai-Gobi, magnitude 7.8 MS, 30 deaths. Great topographical changes, landslides. In the Atai Mountains a rift was found, 250 km long. One mountain range is reported to have increased in height by 6 m. (reference #1003)

December 4, 1957, Mongolia, 45.2 N, 99.2 E, magnitude 8.3 MS. (reference #1212)

December 4, 1957, 03:37:48 UTC, 45.2 N, 99.2 E, magnitude 8.3 MS. Exceptionally violent earthquake recorded at 241 stations and reaching a magnitude of 8.6 (Pasadena).

The devastated area was located in Mongolia in the

eastern Altai mountain system. This vast range,

1,500 km long, is composed of a series of structural

axes; the epicentre was located in the Bogdo Mountains.

This is a sparsely populated region. Several wintering

places were totally destroyed, particularly Dzun

Bogd, Bayan-leg and Barum Bogd. Because the

weather was fine, many shepherds were still on the

pastures with their flocks and had not yet gone to

their winter quarters; this fortunate circumstance

reduced the number of casualties considerably;

according to preliminary estimates there were 20 dead

and 13 missing. Several hundred cattle died from

rockfalls, which often also obstructed the watering

points. The effects of the earthquake in the area we= spectacular and an intensity XI may be given to the pleistoseismic zone. A mission of geologists and seismologists sent from Ulan-Bator travelled through the region a few weeks after the first shock aid thought they had

encountered primaeval chaos. In the IkkeBogdo massif,

peaks had collapsed and rocks were falling with a noise

like thunder; -in Ithe Bakhar Mountains, a section of the earth's surface measuring 15 km long by 800 m

wide had subsided. It was.possible to follow, over a

distance of 300 km, a fault running along the northern

slopes of the mountain range, from the Bayant Sagan

in the west to. the Baga-Bogdo massif in the east.

This enormous fissure, called the Bogdo fault and

comparable to the famots San Andreas fault in

California,'was at places 20 m wide and 2 m deep,

cutting through the basal or crystalline terrains as

well as through the sedimentary terrains. (reference #1040)