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| Titel |
Segmentation of the Izu-Bonin and Mariana slabs based on the analysis of the Benioff seismicity distribution and regional tomography results |
| VerfasserIn |
K. Jaxybulatov, I. Koulakov, N. L. Dobretsov |
| 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 ; 4, no. 1 ; Nr. 4, no. 1 (2013-01-31), S.59-73 |
| Datensatznummer |
250017348
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| Publikation (Nr.) |
 copernicus.org/se-4-59-2013.pdf |
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| Zusammenfassung |
| We present a new model of P and S velocity anomalies in the mantle down to a
depth of 1300 km beneath the Izu-Bonin and Mariana (IBM) arcs. This model is
derived based on tomographic inversion of global travel time data from the
revised ISC catalogue. The results of inversion are thoroughly verified
using a series of different tests. The obtained model is generally
consistent with previous studies by different authors. We also present the
distribution of relocated deep events projected to the vertical surface
along the IBM arc system. Unexpectedly, the seismicity forms elongated
vertical clusters instead of horizontal zones indicating phase transitions
in the slab. We propose that these vertical seismicity zones mark zones of
intense deformation and boundaries between semi-autonomous segments of the
subducting plate. The P and S seismic tomography models consistently display
the slab as prominent high-velocity anomalies coinciding with the
distribution of deep seismicity. We can distinguish at least four segments
which subduct differently. The northernmost segment of the Izu-Bonin arc has
the gentlest angle of dipping which is explained by backward displacement of
the trench. In the second segment, the trench stayed at the same location,
and we observe the accumulation of the slab material in the transition zone
and its further descending to the lower mantle. In the third segment, the trench
is moving forward causing the steepening of the slab. Finally, for the
Mariana segment, despite the backward displacement of the arc, the
subducting slab is nearly vertical. Between the Izu-Bonin and Mariana arcs
we clearly observe a gap which can be traced down to about 400 km in depth. Based
on joint consideration of the tomography results and the seismicity
distribution, we propose two different scenarios of the subduction evolution
in the IBM zone during the recent time, depending on the reference frame of
plate displacements. In the first case, we consider the movements in respect
to the Philippine Plate, and explain the different styles of the subduction
by the relative backward and forward migrations of the trench. In the second
case, all the elements of the subduction system move westward in respect to
the stable Asia. Different subduction styles are explained by the "anchoring"
of selected segments of the slab, different physical properties of the
subducting plate and the existence of buoyant rigid blocks related to sea
mount and igneous provinces. |
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