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| Titel |
Slab seismicity in the Western Hellenic Subduction Zone: Constraints from tomography and double-difference relocation |
| VerfasserIn |
Felix Halpaap, Stéphane Rondenay, Lars Ottemoller |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124358
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| Publikation (Nr.) |
 EGU/EGU2016-3780.pdf |
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| Zusammenfassung |
| The Western Hellenic subduction zone is characterized by a transition from oceanic to
continental subduction. In the southern oceanic portion of the system, abundant seismicity
reaches intermediate depths of 100-120 km, while the northern continental portion rarely
exhibits deep earthquakes. Our study aims to investigate how this oceanic-continental
transition affects fluid release and related seismicity along strike, by focusing on the
distribution of intermediate depth earthquakes. To obtain a detailed image of the seismicity,
we carry out a tomographic inversion for P- and S-velocities and double-difference
earthquake relocation using a dataset of unprecedented spatial coverage in this area. Here we
present results of these analyses in conjunction with high-resolution profiles from migrated
receiver function images obtained from the MEDUSA experiment. We generate tomographic
models by inverting data from 237 manually picked, well locatable events recorded at up to
130 stations. Stations from the permanent Greek network and the EGELADOS
experiment supplement the 3-D coverage of the modeled domain, which covers
a large part of mainland Greece and surrounding offshore areas. Corrections for
the sphericity of the Earth and our update to the SIMULR16 package, which now
allows S-inversion, help improve our previous models. Flexible gridding focusses the
inversion on the domains of highest gradient around the slab, and we evaluate the
resolution with checker board tests. We use the resulting velocity model to relocate
earthquakes via the Double-Difference method, using a large dataset of differential
traveltimes obtained by crosscorrelation of seismograms. Tens of earthquakes align along
two planes forming a double seismic zone in the southern, oceanic portion of the
subduction zone. With increasing subduction depth, the earthquakes appear closer to the
center of the slab, outlining probable deserpentinization of the slab and concomitant
eclogitization of dry crustal rocks. Against expectations, we relocate one robust deep
event at ≈70 km depth in the northern, continental part of the subduction zone. |
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