@misc{KruegerOhrnbergerRoessler2008,
  author    = {Kr{\"u}ger, Frank and Ohrnberger, Matthias and R{\"o}ßler, Dirk},
  title     = {Rupture imaging of large earthquakes with a poststack isochrone migration method},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18395},
  year      = {2008},
  abstract  = {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).},
  language  = {en}
}
@misc{RoesslerKruegerOhrnberger2007,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Rupture propagation of recent large TsE off-coast Sumatra and Java},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13039},
  year      = {2007},
  abstract  = {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.},
  language  = {en}
}
@misc{RoesslerKruegerOhrnberger2008,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Rupture Propagation of the 2008/05/12 Ms8.0 Wenchuan Earthquake},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-29195},
  year      = {2008},
  abstract  = {We study the rupture propagation of the 2008/05/12 Ms8.0 Wenchuan Earthquake. We apply array techniques such as semblance vespagram analysis to P waves recorded at seismic broadband station within 30-100° epicentral distance. By combination of multiple large aperture station groups spatial and temporal resolution is enhanced and problems due source directivity and source mechanism are avoided. We find that seismic energy was released for at least 110 s. Propagating unilaterally at sub-shear rupture velocity of about 2.5 km/s in NE direction, the earthquake reaches a lateral extent of more than 300 km. Whereas high semblance during within 70 s from rupture start indicates simple propagation more complex source processes are indicated thereafter by decreases coherency in seismograms. At this stage of the event coherency is low but significantly above noise level. We emphasize that first result of our computations where obtain within 30 minutes after source time by using an atomized algorithm. This procedure has been routinely and globally applied to major earthquakes. Results are made public through internet.},
  language  = {en}
}
@misc{RoesslerKruegerOhrnbergeretal.2008,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias and Ehlert, Lutz},
  title     = {Automatic near real-time characterisation of large earthquakes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-20191},
  year      = {2008},
  abstract  = {An der Universit{\"a}t Potsdam wird seit 2008 ein automatisiertes Verfahren angewandt, um Bruchparamter großer Erdbeben in quasi-Echtzeit, d.h. wenige Minuten nachdem sich das Beben ereignet hat, zu bestimmen und der {\"O}ffentlichkeit via Internet zur Verf{\"u}gung zu stellen. Es ist vorgesehen, das System in das Deutsch-Indonesische Tsunamifr{\"u}hwarnsystem (GITEWS) zu integrieren, f{\"u}r das es speziell konfiguriert ist. Wir bestimmen insbesondere die Dauer und die Ausdehnung des Erdbebens, sowie dessen Bruchgeschwindigkeit und -richtung. Dabei benutzen wir die Seismogramme der zuerst eintreffenden P Wellen vom Breitbandstationen in teleseimischer Entfernung vom Beben sowie herk{\"o}mmliche Arrayverfahren in teilweise modifizierter Form. Die Semblance wir als {\"A}hnlichkeitsmaß verwendet, um Seismogramme eines Stationsnetzes zu vergleichen. Im Falle eines Erdbebens ist die Semblance unter Ber{\"u}cksichtigung des Hypozentrums zur Herdzeit und w{\"a}hrend des Bruchvorgangs deutlich zeitlich und r{\"a}umlich erh{\"o}ht und konzentriert. Indem wir die Ergebnisse verschiedener Stationsnetzwerke kombinieren, erreichen wir Unabh{\"a}ngigkeit von der Herdcharakteristik und eine raum-zeitliche Aufl{\"o}sung, die es erlaubt die o.g. Parameter abzuleiten. In unserem Beitrag skizzieren wir die Methode. Anhand der beiden M8.0 Benkulu Erdbeben (Sumatra, Indonesien) vom 12.09.2007 und dem M8.0 Sichuan Ereignis (China) vom 12.05.2008 demonstrieren wir Aufl{\"o}sungsm{\"o}glichkeiten und vergleichen die Ergebnisse der automatisierten Echtzeitanwendung mit nachtr{\"a}glichen Berechnungen. Weiterhin stellen wir eine Internetseite zur Verf{\"u}gung, die die Ergebnisse pr{\"a}sentiert und animiert. Diese kann z.B. in geowissenschaftlichen Einrichtungen an Computerterminals gezeigt werden. Die Internetauftritte haben die folgenden Adressen: http://www.geo.uni-potsdam.de/arbeitsgruppen/Geophysik_Seismologie/forschung/ruptrack/openday http://www.geo.uni-potsdam.de/arbeitsgruppen/Geophysik_Seismologie/forschung/ruptrack},
  language  = {en}
}