Presentation on theme: "March 11, 2011, Tohoku-oki Earthquake: preliminary outcomes Tohoku-oki INGV Team - Istituto Nazionale di Geofisica e Vulcanologia – INGV Abstract – On."— Presentation transcript:
March 11, 2011, Tohoku-oki Earthquake: preliminary outcomes Tohoku-oki INGV Team - Istituto Nazionale di Geofisica e Vulcanologia – INGV Abstract – On March 11, 2011 a magnitude 9.0 earthquake hit Honshu island in Japan. The Tohoku-oki giant earthquake occurred near the northeast coast of the island resulting from thrust faulting on or near the subduction zone plate boundary between the Pacific and North America plates. At the latitude of this earthquake, the Pacific plate moves approximately westwards with respect to the North America plate at a rate of 83 mm/yr, and begins its westward descent beneath Japan at the Japan Trench. The March 11 earthquake was preceded by a series of large foreshocks over the previous two days, beginning on March 9th with a M 7.2 event approximately 40 km from the epicenter of the March 11 earthquake, and continuing with another three earthquakes greater than M 6 on the same day. The location, depth, and focal mechanism of the March 11 earthquake are consistent with the event having occurred on the subduction zone plate boundary. Modeling of the rupture of this earthquake indicate that the fault moved upwards of 30-40 m, and slipped over an area approximately 300 km long (along-strike) by 150 km wide (in the down-dip direction). The rupture zone is roughly centered on the earthquake epicenter along-strike, while peak slips were up-dip of the hypocenter, towards the Japan Trench axis. Soon after the earthquake an informal Group of researchers from the Istituto Nazionale di Geofisica e Vulcanologia, called Tohoku-oki INGV Team, decided to share data, processing facilities and scientific capabilities. The aim was to use a multidisciplinary approach to carry on some analysis addressed to achieve added value outcomes.Here we show the data used and the preliminary products. European Geoscience Union General Assembly 2001 - Vienna, Austria, 3-8 April 2011 Displacement field from InSAR and GPS Change detection analysis Seismic source modeling: results Marco Chini and Christian Bignami have processed a strip composed of 13 Envisat frames (track 347, descending orbit) over Honshu island (the result is in the framework of "Tohoku-oki INGV Team", lead by Salvatore Stramondo). The interferogram covers most of the epicentral region and shows a large portion of the surface displacement field. The frames partially overlap so that the overall length is about 800 km. The whole strip has been unwrapped to measure the Line Of Sight surface movement. The maximum displacement reaches about 2.5 m relative to a reference point within the entire frame strip located nearby the southern boundary. In the framework of "Tohoku-oki INGV Team, we applied the SISTEM on the Japan area in order to investigate the ground deformation pattern associated with the March 11, 2011 Tohoku-oki earthquake. We simultaneous integrated the available Envisat and GPS data, and in particular we used (i) the the results of the interferometric process performed by Marco Chini and Christian Bignami (INGV-Rome) and the(ii) GPS data processed at INGV Rome by Nicola DAgostino (Romano et al."Joint inversion of DART buoys and GPS data for the slip distribution of great 2011 Tohoku-oki earthquake", EGU Poster, Vienna April 2011). All original GEONET RINEX data provided to INGV by the Geospatial Information Authority (GSI) of Japan. The figure above shows the preliminary joint model of coseismic slip of the March 11, 2011 Tohoku Earthquake. The fault model has variable dip and strike. We sample the cross-section of the subduction zone geometry analysis carried out by Gavin Hayes. The fault plane is divided into 240 subfaults of 25x25 km. We use the sea-level recordings at 7 deep-sea Bottom Pressure Gauges in open sea (DART) provided by NOAA. We use GPS data processed at INGV Rome using JPL's GIPSY-OASIS software, the kinematic precise point positioning strategy and JPL's Rapid orbit and clock products. The coseismic displacements are calculated as a simple difference of the position estimates averaged 15 minutes before and after the main shock excluding the first 5 minutes during the most intense ground shaking. All original GEONET RINEX data provided by the Geospatial Information Authority (GSI) of Japan. The inversion method is based on a global search technique. We add smoothing and seismic-moment- minimization constraints to the slip distribution. The rupture front is assumed to be circular and propagating at constant speed, fixed at 1.0 km/s, which however needs to be further investigated. This model was generated by F. Romano, A. Piatanesi, S. Lorito, and N. D'Agostino at Istituto Nazionale di Geofisica e Vulcanologia in Rome (Italy). Tsunami modeling performed with COMCOT at CASPUR HPC Center in Rome (Italy). The preliminary distribution of seismic moment release along the modeled source is presented in the figure on the left. Total seismic moment release is 3.95e22 Nm, corresponding to Mw = 9.03. This model naturally implements the seismic source in terms of seismic moment, so that the moment magnitude estimate is not biased by slip-moment conversions. Daniele Melini member of the "Tohoku-oki INGV Team" (lead by Salvatore Stramondo) obtained a preliminary model of seismic moment release of the March 11, 2011 Japan earthquake by modeling GPS displacements with a spherical self-gravitating deformation model (Melini et al., GJI 2008). The model assumes a PREM rheological layering. The fault plane geometry is fixed to USGS seismological estimates. Preliminary GPS time series are provided by the ARIA team at JPL and Caltech.Â All original GEONET RINEX data provided to Caltech by the Geospatial Information Authority (GSI) of Japan. We have retrieved tide gauge data from http://www.ioc-sealevelmonitoring.org/ and analyzed the signal from about 90 tide gauges located in the Pacific and Atlantic oceans. The TG located in the near field of the earthquake, were partially damaged (Tsunami waves arrived at Ofunato at 05:51 UTC, 5 min. after the event. TG is at about 80 km, bottom left figure). Tsunami affected a wide area and wave amplitudes recorded at the tide gauges were also dependent by local effects (i.e. bathymetry). At Crescent City, USA, about 7.500 km far from the epicenter, tsunami waves arrived at 15:30 UTC, 9h 44min after the earthquake, with amplitudes up to 4.5 m. (bottom right figure). At Kawaihae,Hawaii, waves arrived at 13:37 UTC, 7h51m after the event, with amplitudes of about 3 m. Tohoku-oki INGV Team: Tsunami wave propagation Details of the Sendai coastal area affected by tsunami phenomenon. The colour composite representation (RGB) was obtained by combining one pre- (red component) and one co- seismic (green and blue components) SAR intensity correlation images. Red area correspond to damaged region. The entire dataset is composed of 13 ASAR- Envisat frames acquired in three different days: 21/11/2010, 19/02/2011 and 21/03/2011. Amici Stefania, Anzidei Marco, Bignami Christian, Borgstrom Sven, Brunori Carlo Alberto, Buongiorno Fabrizia, Cheloni Daniele, Chini Marco, Cinti Francesca Romana, DAgostino Nicola, De Martini Paolo Marco, De Santis Angelo, Fornaciai Alessandro, Gambino Salvatore, Guglielmino Francesco, Lorito Stefano, Melini Daniele, Merucci Luca, Nappi Rosa, Pantosti Daniela, Piatanesi Alessio, Piscini Alessandro, Puglisi Giuseppe, Riguzzi Federica, Romano Fabrizio, Salvi Stefano, Silvestri Malvina, Siniscalchi Valeria, Vilardo Giuseppe. The Tohoku-oki INGV Team is leaded and coordinated by Stramondo Salvatore. ASTER (Advanced Space-borne Thermal Emission and Reflection Radiometer) is an imaging instrument flying on Terra satellite. It is a part of NASA's Earth Observing System. ASTER is a cooperative effort between NASA, Japan Ministry of Economy, Trade and Industry and the Japan's Earth Remote Sensing Data Analysis Centre. Left figure shows an RGB composite from ASTER bands 3N, 2 and 1 of 19 march 2011, 01:38 UTC. Vegetation is identified by red colour. Right figure shows a classification obtained applying a unsupervised method (k-means) to the ASTER image on left. The Flooding areas are well identified (blue) and involve all coastal area from the harbour up to the airport and more. Furthermore, classification puts in evidence how the tsunami of March 11 has penetrated up to 4 km hinterland. The Tohoku-oki INGV Team thanks Dave Pieri (NASA-JPL) for images provision.
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