 |
| Titel |
Detailed analysis of the Valdes slide: a landward facing slope failure off Chile |
| VerfasserIn |
Andrea Anasetti, Sebastian Krastel, Willy Weinrebe, Ingo Klaucke, Jörg Bialas |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250043597
|
|
|
|
|
|
| Zusammenfassung |
| The Chilean continental margin is a very active area interested by important tectonic
movements and characterized by a fast morphological evolution.
Geophysical data acquired during cruise JC 23, aboard RV JAMES COOK in
March/April 2008 and previous cruises cover most of the active Chilean continental margin
between 33Ë and 37Ë S. Integrated interpretation of multi-beam bathymetric, sub-bottom
profiles, side-scan sonar and seismic data allowed the identification of a number of slope
failures.
The main topic of this project is the morphological and sedimentological analysis of the
Valdes slide, a medium-sized submarine landslide offshore the city of Talcahuano (300 km
south of Santiago). In contrast to most other slides along continental margins, the Valdes slide
is located on the landward facing eastern slope of a submarine ridge. This setting has
important implications for the associated tsunami wave field (first arrival of positive
amplitude).
We measured geometrical parameters of the failure and adjacent slope. The slide affected
an area of 19 km2 between ~1060 m and >1700 m water depths. Its is ~ 6 km long, up to 3
km wide and involved a total sedimentary volume of about 0,8 km3. The failure process was
characterized by a multiple-event and we assume its tsunami potential to be high.
Using the high resolution bathymetric data and the seismic profiles along the slide
deposit it was possible to reconstruct the original morphology of the area in order to
understand the relation between the slide event and the structural evolution of the
ridge.
Through the analysis of the data and bibliographic information about the Chilean margin,
we analyzed potential trigger mechanisms for the landslide. The Valdes slide is situated on a
steep ridge flank. The ridge follows an elongated fault zone running app. parallel to the
margin. This fault zone has a dextral component which in combination with the faults
elongation results in a compressional regime that is superimposed on the overall
subduction-related compression and ultimately generated this ridge. Over-steepening (slope
angle >6Ë ) of rapidly accumulated sediments (high sedimentation rate) and the huge uplift
of the ridge seem to be the most important preconditioning factors of this slide. Seismic data
and core analysis suggest that a weak layer acted as sliding surface. The most likely trigger
can be assumed one of the frequently occurring strong earthquakes in this area. |
|
|
|
|
|
|