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| Titel |
Short-lived tectonic switch mechanism for long-term pulses of volcanic activity after mega-thrust earthquakes |
| VerfasserIn |
M. Lupi, S. A. Miller |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 5, no. 1 ; Nr. 5, no. 1 (2014-01-06), S.13-24 |
| Datensatznummer |
250115251
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| Publikation (Nr.) |
 copernicus.org/se-5-13-2014.pdf |
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| Zusammenfassung |
Eruptive rates in volcanic arcs increase significantly after subduction
mega-thrust earthquakes. Over short to intermediate time periods the link
between mega-thrust earthquakes and arc response can be attributed to dynamic
triggering processes or static stress changes, but a fundamental mechanism
that controls long-term pulses of volcanic activity after mega-thrust
earthquakes has not been proposed yet.
Using geomechanical, geological, and geophysical arguments, we propose that
increased eruption rates over longer timescales are due to the relaxation of
the compressional regime that accompanies mega-thrust subduction zone
earthquakes. More specifically, the reduction of the horizontal stress
σh promotes the occurrence of short-lived strike-slip kinematics
rather than reverse faulting in the volcanic arc. The relaxation of the
pre-earthquake compressional regime facilitates magma mobilisation by
providing a short-circuit pathway to shallow depths by significantly
increasing the hydraulic properties of the system. The timescale for the
onset of strike-slip faulting depends on the degree of shear stress
accumulated in the arc during inter-seismic periods, which in turn is
connected to the degree of strain-partitioning at convergent margins.
We performed Coulomb stress transfer analysis to determine the order of
magnitude of the stress perturbations in present-day volcanic arcs in
response to five recent mega-thrust earthquakes; the 2005 M8.6, 2007 M8.5,
and 2007 M7.9 Sumatra earthquakes; the 2010 M8.8 Maule, Chile earthquake; and
the 2011 M9.0 Tohoku, Japan earthquake. We find that all but one the shallow
earthquakes that occurred in the arcs of Sumatra, Chile and Japan show a
marked lateral component. We suggests that the long-term response of volcanic
arcs to subduction zone mega-thrust earthquakes will be manifested as
predominantly strike-slip seismic events, and that these future earthquakes
may be followed closely by indications of rising magma to shallower depths,
e.g. surface inflation and seismic swarms. |
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