 |
| Titel |
Anatomy of a subduction zone – seismicity structure of the northern Chilean forearc from >100,000 double-difference relocated earthquake hypocenters |
| VerfasserIn |
Christian Sippl, Bernd Schurr |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141910
|
| Publikation (Nr.) |
 EGU/EGU2017-5466.pdf |
|
|
|
|
|
| Zusammenfassung |
| We present a catalog of >100k well-located earthquake hypocenters for the northern Chilean
forearc region, between the latitudes of 18.5∘S and 24∘S. The detected events cover the
timespan 2007-2014 and were extracted from the IPOC permanent station network dataset.
Previously published earthquake catalogs for the region contain significantly fewer
earthquakes. Using this new, high-resolution set of hypocenters, we can outline the slab
structure in unprecedented detail, allowing e.g. the determination of along-strike changes in
slab dip angle or the resolution of structures inside the zone of intermediate-depth
seismicity.
For the compilation of the catalog, we relied on an automated multi-step process for event
detection, association and phase picking. Thus retrieved earthquake hypocenters were then
relocated in a 2.5D velocity model for the Northern Chile forearc region with a probabilistic
approach that also allows the determination of uncertainties. In a final step, double-difference
re-location incorporating cross-correlation lag times was performed, which sharpened event
clusters through relative location.
We estimate that the completeness magnitude of the catalog is around 3. The majority of
all >100k earthquakes are located at intermediate depths (between 80 and 140 km) inside the
subducted slab. This area of pervasive activity extends along the entire strike of the
investigated area, but shows a clear offset at 21∘S, which may hint at a slab tear at this
location. Events of comparable hypocentral depths to the south of this offset are located
further east than the ones to the north of it. Further updip, a triple seismic zone at depths
between 40 and around 80 km is visible, which grades into the highly active event
cluster at intermediate depths: below the plate interface, which is clearly delineated
by seismic activity, a second parallel band of hypocenters only about 5 km below
likely corresponds to earthquakes occurring within the oceanic crust or close to
the oceanic Moho. A third band of earthquakes, paralleling the other two at about
20-25 km below the interface, clearly indicates the presence of seismicity in the
oceanic lithospheric mantle. Seismicity in the upper plate is pervasive throughout
the entire crustal thickness near the coast but gets shallower towards the volcanic
arc. Shallow clusters related to regional mining activities are also clearly visible. |
|
|
|
|
|
|