Task 5 - Fast assessment of source parameters and tsunamigenic potential for M>6 in the Mediterrean region
Objectives
Objective of the project is to detect large earthquakes in the Euro Mediterranean Region, and to discriminate between tsunamigenic and non-tsunamigenic earthquakes.
Epicentral location, focal depth, magnitude and source mechanism are the required earthquake parameters to discriminate between tsunamigenic and non tsunamigenic earthquake.
Epicentral location, focal depth, magnitude and source mechanism are the required earthquake parameters to discriminate between tsunamigenic and non tsunamigenic earthquake.
Activities
In the recent past the MedNet network has contributed to create a robust connection between the seismological network in the region that has lead to create the so called VEBSN (Virtual European Broadband Network) this will be the starting point for creating a virtual network dedicated to the detection of relevant earthquakes and to the estimate of the source parameters with rapid and unmanned techniques.
SeisComP3 and Earthworm will be the data collectors for seismic data coming to several networks around the Mediterranean basin and different techniques as “autoloc” and NonLinLoc will be used for locating earthquakes. The use of different systems working in parallel will also allow to check and validate the most reliable techniques, in term of location accuracy and elapsed time. With the same approach we will explore different Magnitude estimate techniques as Mwp, Mwpd and dominant period, following the experience that comes from different studies of the recent past for the SAFER and other projects.
In the framework of the previous DPC–S4 2005-07 project we established an automatic procedure to quickly estimate the source mechanism of relevant earthquakes in Italy by using the TDMT (Time Domain Moment Tensor) technique. This approach will be extended to the whole Euro Mediterranean region and efforts will be made to automate also the regional CMT (Centroid Moment Tensor).
Because information about the magnitude and location may be not sufficient to assess whether an earthquake can or cannot generate a potentially dangerous tsunami, numerical forward modeling of tsunami propagation is needed. For this reason, we propose to simulate the generation and propagation of tsunamis for many sites which tectonic setting (from geology and fault mechanisms) provides evidence for being place of causative tsunamis. This will allow to build a database of synthetic pre-computed models. In the case of a seismic event, after having determined the location and magnitude of the occurring earthquake, it will be possible to query the database for getting the simulations corresponding to the models closest, both in terms of location and magnitude, to the real case. These models are then interpolated in order to provide an estimation of the wave height for the real source. Thus, this approach will not deal with the detailed modeling of the inundation scenarios but it will only provide first order estimates of the incoming tsunami wave. This approach is similar to that implemented by the Japan Meteorological Agency that is responsible of the tsunami warning system for the Japanese coasts and whose data-base includes about 100,000 synthetic models, and is also shared by the Regional Tsunamis Watch Centres (RTWC) as well as of the National Tsunami Warning Centres (NTWC), that are the fundamental elements of the NEAM Tsunami Warning System currently under development.
The starting point for building the data-base consists in the definition of the characteristics of the earthquakes potentially tsunamigenic, in terms of position, geometrical parameters, and expected magnitude. Moreover, the bathymetry of the sea area of interest has to be known. When these information are available, it is possible to solve numerically the non linear shallow-water equations and to computing the tsunami wave height for all the computational domain, including the coasts. We plan to perform simulations at the Mediterranean scale accounting for the all the known seismic sources having a tsunamigenic potential. In the previous DPC-S2 2005-2007 project some seismogenic structures in the Mediterranean area were investigated for evaluating the effects of the potential tsunamis associated with them on the Italian coasts. We believe that these results could suggest some insights about the main sources to be considered and will use as starting point for building the database. Analogously it is planned the evaluation of tsunami height in a simplified manner by describing the latter into classes according to wave height.
Since a tsunami warning needs to be effectively evaluated and possibly confirmed with observed data, it is proposed to activate a data exchange between the INGV seismic center and the “Servizio Mareografico” of APAT for the data of the “Rete Mareografica Nazionale” (see http://www.idromare.com). Availability of the latter data is expected to spring research on fast determination of tsunami occurrence from the same data. In fact, detection of tsunami signature in sea level records is a very important part toward their validation.
First Annual Meeting: 19-21 October 2009