Monday, April 05, 2010

Earthquake in Ulaanbaatar

"Journalists and the general public rush to any suggestion of earthquake prediction like hogs toward a full trough."

--Charles Richter, creator of the Richter scale for measuring the magnitude of the seismic energy of earthquakes

I received the following message from a Mongolian friend in UB:

"Hello Radigan,
Lately, there are some signs of an earthquake in UB. It will be about an 8-ball and even the president of Mongolia announced a warning to the nation on TV. Looks like it will happen for sure..."

Interestingly, the U.S. Geological Survey has done work in Mongolia studying "earthquakes that occur in the interior of continents far from plate boundaries."

There was earthquake activity in Mongolia in the Twentieth Century, but in western Mongolia, not near UB. The last large earthquake in Mongolia was over 50 years ago, in 1957. If the quakes are cyclical, which they may be, there may not be another large earthquake there for thousands of years:

"The penultimate event on the eastern part of the Bogd strike-slip fault occurred about 2400 years ago, whereas on the western segment only two large earthquakes occurred during the 12,000 years prior to 1957. The Dalan Turuu thrust appears to have slipped every 8000 years on average, the Gurvan Bulag thrust appears to produce earthquakes about every 4000 years, and the Toromhon thrust last moved several tens of thousands of years ago."

--USGS: Earthquake Hazards Program, "1998 USGS Expedition to Mongolia: Previous Work in Mongolia"

Just as there can be earthquakes in San Francisco but not in California's capital city of Sacramento, which is 144 kilometers (90 miles) away, there can be earthquakes in western Mongolia and not in Ulaanbaatar. Charted global earthquake activity shows eastern Mongolia as free of earthquakes as the Amazon and the Sahara:

The multi-organizational Global Seismic Hazard Assessment Program concluded that eastern Mongolia is at relatively low risk of earthquakes, though the Program listed western Mongolia at high risk. Ulaanbaatar sits near the juncture of the risk zones:

Conclusion: It seems unlikely though not impossible that an impending earthquake will strike Ulaanbaatar.

Regarding rumors, it is good to remember that earthquakes cannot be predicted:

There was a 5.1-magnitude earthquake in Dundgov aimag in January that was felt in UB. This event probably fanned earthquake rumors:

There was also a 4.8 earthquake near Lake Khovsgol two weeks ago:

It is noteworthy that there was a similar earthquake rumor in UB in the spring of 2008:


No comments: