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| Titel |
Seismic and aseismic activity associated with the 2008 Mw 6.3 Damxung earthquake, Tibet |
| VerfasserIn |
Lidong Bie, Isabelle Ryder, Stuart Nippress |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074628
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| Zusammenfassung |
| We investigate the 2008 Mw 6.3 Damxung earthquake on the Tibetan Plateau. The main
objectives of this study are (i) to derive a coseismic slip model in a layered elastic Earth; (ii)
to test whether afterslip is spatially and temporally correlated with aftershocks; (iii)
to constrain the lower bound of mid-crustal viscosity. The fault parameters and
coseismic slip model are derived by joint inversion of Envisat data. We developed a new
Monte Carlo nonlinear inversion scheme with a layered crust. Compared to the
slip distribution obtained with a homogeneous crustal model, the maximum slip is
smaller and deeper, while the moment release calculated from both models are
similar.
Postseismic deformation time series constructed from 17 interferograms covering 665 days
after the main shock reveals localised deformation at the southern part of the fault. Afterslip
inversions indicate three localised slip patches, and the cumulative afterslip moment after 615
days is at least ~11% of the coseismic moment.
We obtained aftershock data from the China Earthquake Data Centre, which provides phase
information, magnitude and location as recorded by a local network until the end of 2008, for
Ml > 1 aftershocks. We apply the Joint Hypocentral Determination method to relocate Ml > 3
aftershocks, most of which occurred within 20 days after the mainshock, before
the first postseismic SAR acquisition. Using the centre of the InSAR-derived slip
distribution as a fixed location, we test the spatial relationship between coseismic
slip, afterslip and relocated aftershocks. We find that the aftershock distribution
matches the coseismic slip distribution well, in contrast to the overlapping relationship
found by D’Agostino et al. (2012) for the 2009 L’Aquila earthquake. The observed
relationship for the Damxung case implies that the afterslip and aftershocks do not obey
certain space-time relationships inferred in other studies of different earthquakes. We
note, however, that since our InSAR postseismic time series starts 20 days after the
Damxung earthquake, there is a possibility that the very early afterslip pattern looked
different.
We also carry out modeling of viscoelastic relaxation in a Maxwell half-space to constrain
the lower bound of mid-crustal viscosity. By calculating the RMS misfit of the
residual between observed and modelled postseismic displacements using a range
of viscosities, we infer a lower bound of 1 Ã 1018 Pa s. This is consistent with
viscosity estimates in other studies of postseismic deformation across the Tibetan
Plateau.
1. D’Agostino, N., Cheloni, D., Fornaro, G., Giuliani, R., & Reale, D. (2012). Space-time
distribution of afterslip following the 2009 L’Aquila earthquake. Journal of Geophysical
Research, 117(B2), B02402. |
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