Abstract

The mega-thrust Mw=9.3 earthquake that occurred early morning on 26/12/2004 off-coast Sumatra, Indonesia, caused a giant tsunami. The tsunami devastated vast coastal areas surrounding the Indian Ocean causing over 280,000 fatalities. This earthquake has been the largest recorded earthquake on earth since the Mw=9.5 Chile event in 1960. It had a duration of at least 430 s and a rupture length over 1,150 km. Applying standard array methods the duration and the extent of the rupture front could be successfully determined using the large aperture seismic arrays GRSN (Germany) and FNET (Japan) (Krüger and Ohrnberger, 2005; 2006). Within this project the used methods will be improved and further developped to enable their application in a real-time fashion. This will allow rapid estimation of the extent and the direction of the propagating rupture for large earthquakes. Our activities will be first focused on earthquakes in the Indian Ocean to improve Tsunami forecasting in the region. The method will be a sensor component of GITEWS - the German Indonesian Tsunami Early Warning System.

Near-real-time data processing/ Documentation of major recent events


Major earthquakes in the Sunda Arc region since 2000

Bengkulu 2007091211 Sumatra 20080225 Sumatra 2007091223 Sumatra 20070913 Sumatra 20041226 Sumatra 20041226 Java 20070808 20071024 Sumatra Bengkulu Java 200607

Figure: Interactive map of Sumatra and Java. By Clicking on the fault-plane-solutions rupture details of the event may be viewed. Red stars: epicentres of large earthquakes (M>7.5) with year and magnitude (USGS). Highlighted patches show areas of seismic energy realse during earthquake rupturing.

Tracking the rupture of the July 17, 2006, Mw=7.7 tsunamogenic earthquake off-coast Yogyakarta, Indonesia

On July 17, 2006 a Mw=7.7 earthquake (magnitude determined by USGS) shock the Indian Ocean. It occurred at about 20 km depth off-coast Badung, Indonesia. The earthquake mechanism shows thrusting on a NE-SW striking fault. It caused a local tsunami with wave heights exeeding 2 m. The death toll reached several hundred. Thousands of people were displaced. A tsunami alert was given by the Pacific Tsunami Warning Center.
We have been investigating the propagation and the extent of the rupture front of the causative earthquake.

Preliminary results

For determination of the ruptured area we use seismograms recorded at broadband stations at teleseismic distances and array methods by Krüger and Ohrnberger, 2005, 2006 (see references below). Magenta lines show epicentral distance in 30° intervals. For data provision we acknowledge FNET, Japan and IRIS.


Increased semblance values indicate areas where seismic energy is released by earthquake rupturing. The ruptured area extends from the epicentre (star) to the SE (compare also finite-fault solutions by USGS).
The figure shows a snapshot of the semblance and the track of the semblance maxima at 08:20:05 (UTC) on 17/07/2006, 125s from start of the study. Watch our ANIMATION (18 MB) to see the complete time series of the semblance. Rupturing starts at about 90 s in the animation. The red line shows major fault zones. The trench at which the subduction of the Indioustralian under the Eurasian plate occurs and where the studied earthquake is located is situated off-coast Indonesia.

[ANIMATION (18 MB)] of the semblance analysis to illustrate the spatio-temporal propagation of the rupture front. The animation starts 90 s before the onset of the event.

[LARGE] figure


Snapshot of the cumulative semblance indicating the extent of the ruptured area at 08:22:55 (UTC) on 17/07/2006, 300 s after the start of the study. Cicles indicate aftershocks within three days following the event. Watch our ANIMATION (18 MB) to see the complete time series of the cumulative semblance. Rupturing starts at about 90 s.

[ANIMATION (18 MB)] of the cumulative semblance to illustrate the extent of the ruptured area as a function of rupture time. The animation starts 90 s before the onset of the event.

[LARGE] figure


The duration of the July 17, 2006 event was at least 130 s as estimated from increased semblance values.

[ENLARGED] figure

Tracking the rupture of the Mw=9.3 giant Sumatra tsunamogenic earthquake off-coast Yogyakarta, Indonesia, on 26/12/2004

Tracked rupture of the Mw=9.3 giant Sumatra earthquake on 26/12/2004 that initiated a vast tsunami causing more than 280,000 fatalities and devastating large coastal areas surrounding the Indian Ocean. View from top- West. [enlarged figure, 0.8 MB] [animation - AVI file, 13 MB] view from West
Observations of the stress field in the Indian Ocean and around Indonesia (obtained from the WSM project) [enlarged figure, 0.05 MB] view from West

Veröffentlichungen / Publications
Krüger, F., Ohrnberger, M., 2006, Spatio-temporal source characteristic of the 26 December 2004 Sumatra earthquake as imaged by teleseismic broadband arrays, Geophys. Res. Lett., 32, doi:10.1029/2005GL023939
Krüger, F., Ohrnberger, M., 2005, Tracking the rupture of the Mw=9.3 Sumatra earthquake over 1,150 km at teleseismic distance, Nature, 435, 937-939, doi:10.1038/nature03696
Konferenzbeiträge /Conference Contributions
Roessler, D., Krueger, F., Ohrnberger, M., 2008, Automatic near real-time characterisation of large earthquakes, (Internal) GITEWS Annual Project Meeting, 29. -30. April, Potsdam [Poster]
Lipke, K., Krueger, F., Roessler, D., Ohrnberger, M., 2008, Subduction zone structure along Sumatra from receiver functions, (Internal) GITEWS Annual Project Meeting, 29. -30. April, Potsdam [Poster]
Roessler, D., Krueger, F., Ohrnberger, M., 2008, Rupture characteristics of large earthquakes (M>7) along the Sunda Arc since 2004, SSA 2008 Annual Meeting, Santa Fe, USA [Vortrag (PDF, 2.1 MB)]
Krueger, F., Ohrnberger, M., Roessler, D., 2008, Rupture Imaging of Large Earthquake with a Post-stack Isochrone Migration Method , EGU meeting, Vienna, Austria [Poster]
Roessler, D., Krueger, F., Ohrnberger, M., 2008, Rupture details of tsunamogenic and non-tsunamogenic large earthquakes along the Sunda Arc, DGG Annual Meeting, Freiberg [Vortrag (PDF, 2.3 MB)]
Lipke, K., Zitzmann, Ma., Amberger, M., Ehlert, C., Rößler, D. ; Krüger, F., Ohrnberger, M., 2007, Traveltime residuals at regional and teleseismic distances for SE-Asia, (Internal) GITEWS Annual Project Meeting, 14 - 15 June, Potsdam [Poster]
Rößler, D., Krüger, F., Ohrnberger, I., 2007, Rupture propagation of recent large TsE off-coast Sumatra and Java, EGU Meeting, 15 - 20 April, Vienna, Austria [Poster]
Rößler, D., Krüger, F., Ohrnberger, I., 2007, Rupture propagation of the TsE (Mw7.7) on 17 July 2006 off-coast Java, DGG Tagung, 26 - 29 March, Aachen, Germany [Poster]
Krüger, F., Rößler, D., Ohrnberger, M., 2006, Rupture propagation of the July 17, 2006, Mw=7.7 TsE off-coast Java, AGU Fall Meeting 11 - 15 December, San Francisco/USA, [Poster, PDF 17 MB]
Externe Quellen / External sources
GEOFON
GFZ: distribution of aftershocks following the the mega earthquake in Sumatra on December 26, 2004
USGS: momemt-tensor solution of the December 26, 2004, event

 

 

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