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[Earth Sciences] Academia Sinica Earth Scientists Show Slow Earthquakes Triggered by Typhoons at the Journal <i>Nature</i>

Posted by gustav 
[Earth Sciences] Academia Sinica Earth Scientists Show Slow Earthquakes Triggered by Typhoons at the Journal Nature (Chinese Version)

Academia Sinica Newsletter (2009/06/11) Scientists from Academia Sinica's Institute of Earth Sciences (IES) and the Department of Terrestrial Magnetism of the Carnegie Institution of Washington have made a surprising discovery that slow earthquakes are triggered by typhoons. The findings are published in Nature (Volume 459 Number 7248) on 11th-Jun.

During a four-year study period from August 2003 to August 2007, these researchers identified 20 slow earthquakes, non-violent fault slippage events that take hours or days instead of a few brutal seconds to minutes to release their potent energy.

"In this study, we monitored deformation in eastern Taiwan using three highly sensitive borehole strainmeters located about 5 to 15 km apart, installed 200-270 meters deep. These devices detect otherwise imperceptible movements and distortions of rock," explained the first author Dr. Chiching LIU.

In order to make the observation precise, the researchers have to keep the data of atmospheric pressure variation so that the factor thereof in the subterranean rock's changes could be reduced. Surprisingly they found that eleven of the 20 slow earthquakes coincided with typhoons and were also stronger and characterized by more complex waveforms than the other slow events. The scientists discovered that the reduced atmospheric pressure caused by the typhoons unclamps the fault, triggering slow quakes.

"Typhoons reduce the atmospheric pressure on land, but do not affect conditions at the ocean bottom, because water moves into the area and equalizes the pressure," explained one of the coauthors of the Nature article, Dr. Selwyn SACKS, of the Department of Terrestrial Magnetism at Carnegie. " The reduction in pressure above one side of an obliquely dipping fault tends to unclamp it."

"These data are unequivocal in identifying typhoons as triggers of these slow quakes. The probability that they coincide by chance is vanishingly small," remarked another coauthor Dr. Alan LiINDE of Carnegie.

The group now intends to expand their instrumentation and monitoring to different tectonic regimes of the same plate boundary in eastern Taiwan.

The publication entitled " Slow Earthquakes Triggered by Typhoons" Nature Volume 459 Number, 7248 (2009) can be found at the Nature website: http://www.nature.com/nature/journal/v459/n7248/full/nature08042.html
The complete list of authors is: Chiching LIU, Alan T. LINDE and I. Selwyn SACKS.

Media contacts:
Dr. Chiching LIU Institute of Earth Sciences, Academia Sinica, liucc@sinica.edu.tw
(Tel)+886-2-27839910 Ext. 517
Ms. Mei-Hui LIN, Public Relations Office, Central Office of Administration mhlin313@gate.sinica.edu.tw
(Tel)+886-2-2789-8821, (Fax)+886-2-2782-1551, (M) 0921-845-234


Further Information:
Academia Sinica Newsletter 2009/06/11