Geophysics

Rumbles After Rain

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Science  10 Nov 2006:
Vol. 314, Issue 5801, pp. 897
DOI: 10.1126/science.314.5801.897b

Water buried in the earth has appeared to cause earthquakes beneath certain reservoirs and in other areas with fluctuating groundwater levels. The fluid is thought to lubricate faults and alter pressure, thus making it easier for rocks to slip. Hainzl et al. have monitored seismic signals from the landscape surrounding Mount Hochstaufen in southeastern Germany, and they find that minor earthquake swarms tend to follow periods of high precipitation there. Seismic activity has been observed in this range of limestone and dolomite mountains for some 600 years, although such behavior is unusual in the wider region. The earthquakes tend to be small but numerous: approximately 1100 small shallow earthquakes (with moment magnitudes less than 2.4) were detected by a seismic array in 2002. Most earthquakes occurred in the summer months, particularly after wet periods in March and August. The resulting seismic events correlate in space and time with the calculated distribution of pore pressure changes due to diffusing rainwater and the frictional behavior of faults. The seismicity data indicate the sensitivity of the Earth's crust to local disturbances and offer a potential means of predicting earthquakes on the basis of weather patterns in such regions. — JB

Geophys. Res. Lett. 33, L19303 (2006).

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