Geophysics

Bohemian Rhapsody in the Crust

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Science  24 Jan 2003:
Vol. 299, Issue 5606, pp. 475
DOI: 10.1126/science.299.5606.475d

Swarms of earthquakes with small to moderate magnitudes are often associated with volcanic activity. In the Vogtland/northwest Bohemia region of the western Bohemian Massif along the Germany-Czech Republic border, major swarms with a periodicity of 74 years have been recorded since the 1550s, yet there has been no volcanic activity in this area for 100,000 years.

A special issue introduced by Jentzsch et al. synthesizes recent measurements of the 10,000 events during the autumn of 2000 and provides a better understanding of this recurrent crustal rhapsody. Enhanced seismic and geodetic data, as well as stress-field modeling, indicate that the swarms are driven by magmatic fluid migration and degassing along specific areas of fault zones. Perhaps most intriguingly, a hydrologic study by Koch et al. showed changes in water well levels and mineral springs (Bad Brambach) chemistry over a 4- to 5-week period before the seismicity began, due to an unusually prolonged buildup of fluid pressure. During and after the swarm, a large flux of CO2 degassing was detected south of the fault zone. — LR

J. Geodynamics35, 1; 107 (2003).

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