 |
| Titel |
The Fine Structure of the Subducted Investigator Ridge in Western Sumatra |
| VerfasserIn |
Dietrich Lange, Frederik Tilmann, Andreas Rietbrock, Rachel Collings, Danny Natawidjaja, Bambang Suwargadi, Tim Henstock, Trod Ryberg |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250038774
|
|
|
|
|
|
| Zusammenfassung |
| The Sumatran margin played host to three great earthquakes in the recent past (Aceh-Andaman
26 December 2004 Mw=9.2, Nias 28 March 2005 Mw=8.7, Bengkulu 12 September 2007
Mw=8.5). Here we present local earthquake data from a dense, amphibious local seismic
network from an unbroken segment of the Sumatran margin where the Investigator fracture
zone (IFZ) subducts beneath the Sumatran mainland. The rare occurrence of forearc islands
along the Sumatran margin allows the deployment of seismic land stations above the shallow
part of the thrust fault. In combination with ocean bottom seismometers this geometry
provides high hypocenter location quality for the updip end of the seismogenic zone in an
area where geodetic data are also available. More than 1700 local events with magnitudes
between 1 to 5.7 Ml (41.000 arrivals) were observed between April 2008 and February
2009. We present the seismicity distribution of this segment boundary based on a
minimum 1-D velocity model and relate it to the background seismicity. Furthermore
we will present first results of local tomography inversion techniques and focal
mechanisms.
The downgoing Benioff zone is readily identifiable as an north-east dipping plane down
to a depth of 225 km. West of Nias a trench parallel, 25 km wideband of seismicity is
observed; this seismicity occurs updip of the 2005 event. South of Nias the spatial
distribution of seismicity is irregular: shallow seismicity in seismogenic depths is highly
concentrated forming well-defined clusters. Shallow seismicity related to the mega-thrust
shows pronounced nests of seismicity below the trench at 0.1°N and 30 km north of the
westernmost Batu Islands. Very sparse seismic activity below Siberut island reflects
the locked state of the plate interface which ruptured last in 1797. In total, three
NNE trending bands of seismicity can be identified in the deeper ( |
|
|
|
|
|
|