Naslov
The puzzle of the Bardarbunga, Iceland earthquake: No volumetric component in the source mechanism

Autori
Tkalčić, Hrvoje ; Dreger, D.S. ; Foulger, G.R. ; Julian, B.R.

Izvornik
Bulletin of the seismological society of america (0037-1106) 99 (2009), 5; 3077-3085

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
volcanic earthquake; Bárdarbunga

Sažetak
A volcanic earthquake with Mw 5:6 occurred beneath the Bárdarbunga caldera in Iceland on 29 September 1996. This earthquake is one of a decade-long sequence of M 5
events at Bárdarbunga with non-double-couple mechanisms in the Global Centroid Moment Tensor catalog. Fortunately, it was recorded well by the regional-scale Iceland Hotspot Project seismic experiment. We investigated the event with a complete moment tensor inversion method using regional long-period seismic waveforms and a composite structural model. The moment tensor inversion using data from stations of the Iceland Hotspot Project yields a non-double-couple solution with a 67% vertically oriented compensated linear vector dipole component, a 32% doublecouple component, and a statistically insignificant (2%) volumetric (isotropic) contraction. This indicates the absence of a net volumetric component, which is puzzling in the case of a large volcanic earthquake that apparently is not explained by shear slip on a planar fault. A possible volcanic mechanism that can produce an earthquake without a volumetric component involves two offset sources with similar but opposite volume changes. We show that although such a model cannot be ruled out, the circumstances under which it could happen are rare.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA