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Microseismic multiplets in the northeastern Bohemian Massif

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ŠPAČEK Petr ZACHERLE Pavel SÝKOROVÁ Zdeňka PAZDÍRKOVÁ Jana

Druh Článek v odborném periodiku
Časopis / Zdroj Zeitschrift für Geologische Wissenschaften
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
Obor Seismologie, vulkanologie a struktura Země
Klíčová slova microseismicity; seismic multiplets; correlation; active tectonics; pull-apart; Sudetic Fault System; Bohemian Massif
Popis We have analysed >1800 records of very weak microearthquakes (-1.9<=ML<=2.2) registered in the NE part of the Bohemian Massif during the years 1998-2008. Cross-correlation analysis showed that 74% of these events are duplets and multiplets or near-multiplets. 191 families of these similar events were distinguished, representing small-volume repeatedly activated focal domains. The families are largely variable in terms of number of events (2-101), overall durations of activity (up to >12 years) and time distributions of the events. The magnitude-distribution of events from individual re-activated foci obeys Gutenberg-Richter law at least in the magnitude range -1.3<=ML&<=1.3. The typical b-values are close to b=1, which also applies for the whole catalogue of events located in the region. In this respect, the investigated region is similar to other presently deformed regions where seismicity is controlled by far-field stresses. Based on the fault geometry, the evolution of sedimentary basin in the most active part of the region, and the spatial co-incidence of the earthquake epicentres with carbonated mineral springs in a rhomb-shaped domain, we suggest a preliminary model explaining the studied region as a transfer zone with releasing geometry (pull-apart mechanism), operating within the system of dextral wrench faults.