Mongolia Earthquake – July 9, 1905

A vast area of two million square miles was damaged by this earthquake and the shaking was felt over a distance of 1,500 miles.

On July 9, 1905, an earthquake of magnitude 8.4 occurred in the Gobi–Altai region of southwestern Mongolia, close to the Chinese border. At that time very little was known or documented about geological changes in that part of the world. This catastrophic event in 1905 was an exception. It was one of the very few for which detailed data was available. An aftershock of almost the same magnitude occurred in the same location two weeks later.

A land area in parts of Mongolia, China, and Russia, covering as much as two million square miles, was affected by these events and people experienced the shaking from east to west over a distance of 1,500 miles. A large number of rocks rolled down from the 12,000 feet high surrounding mountains, trees were uprooted, and two lakes, each of eight acres in size, disappeared.

Deep fissures, one stretching for seventy-five miles and another for two hundred miles, formed in the wake of the July earthquakes and from within these fissures water was forced out on to the surface. Subsequent research, mainly in modern times after World War II, identified a series of earthquakes subsequent to the 1905 quake. One occurred in 1931, one in 1957, and one in 1967, each one of magnitude 8 or greater, a rare record in the history of earthquakes anywhere in the world. Additionally, each one of these events gave rise to fault movements as big as twenty feet and rupture lengths of several hundred miles. How could so many catastrophic earthquakes occur within a single century and within two hundred miles of one another?

Geologists have concluded that, in this poorly understood region, events like these appeared in cycles over geological time with recurrence rates of several thousands of years. All of the information we now have about the 1905 event came from one Russian seismologist who traveled to the area of the earthquake at his own expense, in 1905, and by primitive means of transportation. His notes and maps lay in the archives of the Russian Geographic Society until they were discovered in 1957. With the data from 1905 available to them in 1957, and encouraged by the new interest in eastern Siberia by political leaders, geologists began to study the Gobi–Altai region in greater detail than had ever been previously attempted. U.S. geologists in particular saw similarities between the layout of fault lines in this part of Mongolia and the fault lines associated with the Venture and the San Andreas faults.

In particular they saw that what had happened in the Gobi–Altai earthquake, namely the simultaneous rupturing of two major faults, were to happen in California, it would be worse than anything that had yet hit that state. The new interest in the Gobi–Altai Region enabled the geological societies of Russia, China, and Mongolia to work together in the investigation of the 1957 earthquake when it struck. A year later the Academy of Sciences of the USSR, the name of the country at that time, appointed a group of geologists to investigate the Gobi–Altai area, to map it in detail and to carry out seismological investigations over a large area.