TY - GEN A1 - Rößler, Dirk A1 - Krüger, Frank A1 - Ohrnberger, Matthias T1 - Rupture propagation of recent large TsE off-coast Sumatra and Java N2 - The spatio-temporal evolution of the three recent tsunamogenic earthquakes (TsE) off-coast N-Sumatra (Mw9.3), 28/03/2005 (Mw8.5) off-coast Nias, on 17/07/2006 (Mw7.7) off-coast Java. Start time, duration, and propagation of the rupture are retrieved. All parameters can be obtained rapidly after recording of the first-arrival phases in near-real time processing. We exploit semblance analysis, backpropagation and broad-band seismograms within 30°-95° distance. Image enhancement is reached by stacking the semblance of arrays within different directions. For the three events, the rupture extends over about 1150, 150, and 200km, respectively. The events in 2004, 2005, and 2006 had source durations of at least 480s, 120s, and 180s, respectively. We observe unilateral rupture propagation for all events except for the rupture onset and the Nias event, where there is evidence for a bilateral start of the rupture. Whereas average rupture speed of the events in 2004 and 2005 is in the order of the S-wave speed (≈2.5-3km/s), unusually slow rupturing (≈1.5 km/s) is indicated for the July 2006 event. For the July 2006 event we find rupturing of a 200 x 100 km wide area in at least 2 phases with propagation from NW to SE. The event has some characteristics of a circular rupture followed by unilateral faulting with change in slip rate. Fault area and aftershock distribution coincide. Spatial and temporal resolution are frequency dependent. Studies of a Mw6.0 earthquake on 2006/09/21 and one synthetic source show a ≈1° limit in resolution. Retrieved source area, source duration as well as peak values for semblance and beam power generally increase with the size of the earthquake making possible an automatic detection and classification of large and small earthquakes. KW - Tsunami KW - Erdbeben KW - Indischer Ozean KW - Bruchausbreitung KW - Seismologie KW - Tsunami KW - Earthquake KW - Indonesia KW - Indian Ocean KW - Rupture Propagation KW - Seismology Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13039 ER - TY - JOUR A1 - Rößler, Dirk A1 - Krüger, Frank A1 - Ohrnberger, Matthias T1 - Rupture propagation of the TsE (Mw7.7) on 17 July 2006 off-coast Java N2 - The Mw=7.7 tsunamogenic earthquake (TsE) on 17 July 2006, 08:19:28 shock the Indian Ocean at about 15 km depth off-coast Java, Indonesia. It caused a local tsunami with wave heights exceeding 2 m. The death toll reached several hundred. Thousands of people were displaced. By means of standard array methods, we have investigated the propagation and the extent of the rupture front of the causative earthquake. Waveform similarity is expressed by means of the semblance. We back-propagate the semblance for first-arrival phases recorded at broad-band stations within teleseismic distances (30°-95°). Image enhancement is realised by stacking the semblance of 8 arrays within different epicentral and azimuthal directions. From teleseismic observations we find rupturing of a 200 x 100 km wide area in at least 2 phases with propagation from NW to SE and source duration >125 s. The event has some characteristics of a circular rupture followed by unilateral faulting with change in slip rate. Unusually slow rupturing (≈1.5 km/s) is indicated. Fault area and aftershock distribution coincide. Spatial and temporal resolution are frequency dependent. Studies of a Mw6.0 earthquake on 2006/09/21 and one synthetic source show a ≈1° limit in resolution. Retrieved source area, source duration as well as peak values for semblance and beam power increase with the size of the earthquake making possible an automatic detection and classification of large and small earthquakes. KW - Seismologie KW - Erdbeben KW - Tsunami KW - Indischer Ozean Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12964 ER - TY - JOUR A1 - Lipke, Katrin A1 - Zitzmann, Max A1 - Amberger, Manuel A1 - Ehlert, Carsten A1 - Rößler, Dirk A1 - Krüger, Frank A1 - Ohrnberger, Matthias T1 - Traveltime residuals at regional and teleseismic distances for SE-Asia N2 - Traveltime residuals for worldwide seismic stations are calculated. We use P and S waves from earthquakes in SE-Asia at teleseismic and regional distances. The obtained station residuals help to enhance earthquake localisation. Furthermore we calculated regional source dependent station residuals. They show a systematic dependence of the locality of the source. These source dependent residuals reflect heterogenities along the path and can be used for a refinement of earthquake localisation. N2 - Laufzeitresiduen für weltweite seismische Stationen werden berechnet. Wir nutzen P - und S-Wellen von Erdbeben in Südostasien in teleseismischen und regionalen Distanzen. Die so erhaltenen Stationsresiduen helfen, die Lokaliesierung von Erdbeben zu verbessern. Außerdem berechnen wir regional quellabhängige Stationsresiduen. Diese zeigen eine systematische Abhänbgigkeit vom Ort der Quelle. Sie spiegeln Heterogenitäten entlang des Strahlweges wieder und können für eine Verfeinerung der Ersbebenlokaliesierung genutzt werden. KW - Seismologie KW - Südostasien KW - Laufzeitresiduen KW - GITEWS KW - Wellengeschwindigkeiten KW - seismology KW - Southeast Asia KW - traveltime KW - residuals KW - GITEWS Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14117 ER - TY - GEN A1 - Krüger, Frank A1 - Ohrnberger, Matthias A1 - Rößler, Dirk T1 - Rupture imaging of large earthquakes with a poststack isochrone migration method N2 - Rapid and robust characterization of large earthquakes in terms of their spatial extent and temporal duration is of high importance for disaster mitigation and early warning applications. Backtracking of seismic P-waves was successfully used by several authors to image the rupture process of the great Sumatra earthquake (26.12.2004) using short period and broadband arrays. We follow here an approach of Walker et al. to backtrack and stack broadband waveforms from global network stations using traveltimes for a global Earth model to obtain the overall spatio-temporal development of the energy radiation of large earthquakes in a quick and robust way. We present results for selected events with well studied source processes (Kokoxili 14.11.2001, Tokachi-Oki 25.09.2003, Nias 28.03.2005). Further, we apply the technique in a semi-real time fashion to broadband data of earthquakes with a broadband magnitude >= 7 (roughly corresponding to Mw 6.5). Processing is based on first automatic detection messages from the GEOFON extended virtual network (GEVN). KW - Seismologie KW - Erdbeben KW - Array Seismologie KW - Migration KW - Seismology KW - Earthquake KW - Array Seismology KW - Migration Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18395 ER -