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Titel |
Vp, Vs, and Vp/Vs distribution in the crust and uppermost mantle beneath Northeastern Japan derived from tomographic inversion of regional data from JMA catalogue |
VerfasserIn |
K. Gadylshin, I. Koulakov |
Konferenz |
EGU General Assembly 2009
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 11 (2009) |
Datensatznummer |
250019316
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Zusammenfassung |
In this study, we revise the data on local seismicity in the Northeastern Japan area
recorded by JMA. We have applied the newest version of the LOTOS-07 algorithm,
which includes absolute source location, optimization of the starting 1D velocity
model, and iterative tomographic inversion for 3D seismic P, S velocities, Vp/Vs
ratio and source parameters. Special attention is paid to verification of the obtained
results. In order to estimate the random factors, we have performed the odd\even test,
which consist in independent inversion of two data subsets. Comparison of the
inversion results demonstrates good correlation for both the P and S models, and
demonstrates that the result is rather robust and is almost unaffected by random factors. For
investigating the resolution of Vp and Vs anomalies, we have performed horizontal and
vertical checkerboard tests. For real and synthetic data, we have estimated the best
reference models. We considered a few different starting models and estimated their
effect upon the inversion results. As a result of simultaneous inversion of real data
we have obtained locations of earthquakes in the study area and distributions of
Vp, Vs and Vp/Vs ratio in the crust and the uppermost mantle. Deep seismicity is
aligned along the subducted Pacific plate and forms double seismic zone of ~40km
thickness. At shallow depths seismicity marks the main regional faults in the crust.
P and S velocity models show clear low velocity in the onshore areas and high
velocity in the offshore areas, which can be due to compositional differences between
continental and oceanic crust. The lowest velocities and highest Vp/Vs ratio are
observed beneath zones of recent volcanism. In the uppermost mantle we observe low
velocity patterns which link these volcanic zones with deep seismicity clusters. |
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