Objectives: Deployment of 5 Ocean Bottom seismometers to integrate the on land seismic network. These OBS are produced by INGV Gibilmanna Observatory and had been tested only twice: the prototype was deployed in the Tyrrhenian sea near the Marsili spreading centre and very recently three OBS were deployed in the Ionian sea, two of them were just recovered.
The production of itlian OBS opens new frontiers to itlian seismologist and make possible an important marine development of the National Seismic Network. Up to now our OBS are stand-alone but during the Messina deployment we would like to test an acoustic link to recover data without recovering the instruments from the sea floor.

Activities: In this project we would like to have OBS instruments deployed for a total of about 12/18 months with a first deployment and recovery of the five OBS in selected site with proper bathymetric properties, in the first year and a re-deployment of instruments in the second year.
During the second deployment the acoustic link will be tested. Two of these OBS were just recovered from the Ionian sea and the data recorded will be used to become confident in the analysis of OBS signals. The continuous recordings from OBS seismometers will be integrated in the project data archive.

Methodologies: To deploy and recover the marine seismographs an appropriate ship will be rented twice; each cruise will last about two-three days. OBS are equipped with sensors Trillium 120 sec, and hydrophone (DPG band pass 160 s -2Hz), power supply, double recovery system and acquisition system on compact flash of 24 GB.

Objectives: Main goal of this WP is the creation of a waveform archive that will collect, in a uniform format, recordings of all the available seismic stations present in the region. It will be the first example of complete integration of permanent networks (National Seismic Network; Peloritni Local network), temporary deployments (both mobile network from INGV CNT and INGV CT) and OBS data, that hopefully will become a standard for INGV seismic experiment.
We will get refined location to define seismogenic structures inside the Messina Strait and in the surrounding region especially in the Tyrrhenian and Ionian sea. We will evaluate the improvement introduced by the use of OBS on the seismic detection and on earthquakes location

Activities: To build the archive we should convert all the continuous seismic recordings (permanent stations, temporary stations and OBS) in a uniform format. To archive all the permanent networks we need to open a new real-time link between INGV CNT (Rome) and INGV Catania to let enter into the data-base the data of the local network of Peloritni. Temporary stations and OBS data are integrated with real time data every time they are collected. Starting from these continuous recordings of the integrated network a semiautomatic procedure will define the triggers and the P and S arrivals (this procedure is implemented in Task 1 - WP1.1) to locate the seismicity using both conventional and refined techniques. The microseismicity recorded will delineate the presence of seismogenic structures in the study area which will help in understanding the seismotectonics of the area.

Methodologies:To build the archive we will take advantage of personnel, structures and experience of the National Seismic Network run by INGV. We are developing standard procedure to convert all the gathered data in SEED format and to build a common open data-base for the researches; this will become a standard for experiments done using INGV portable stations. To detect triggers and to pick phases we are going to use procedures developed in the past year (funding DPC 2004-2006) and implemented in Task1 WP1.1. The earthquakes will be located using standard, double- differences techniques, in collaboration with WP 2.5 (UR University of Messina); special attention will have doublets and repeated earthquakes, which are important for the WP2.3 analysis.

Objectives: The study of seismic anisotropy in the crust and uppermost mantle help defining the deformation field of the medium sampled by the seismic waves. In particular the anisotropic parameters in the crust individuate the fracture field geometries connected with the active stress field. If anisotropy is caused by the presence of fluid-saturated microcracks or fractures, aligned or opened by the active stress field, the S waves polarized parallel to the direction of maximum horizontal stress are faster than the one polarized in the orthogonal direction, as suggest by the extensive-dilatancy anisotropy model (EDA), and the difference in velocity is a measure of the intensity and/or thickness of the fracture field.
Among the various studies (definition of velocity and attenuation structure; definition of seismic discontinuities etc.) that will be done on the databank, produced by WP 2.2, we decide to include the study of seismic anisotropy in this project because together with the evaluation of focal mechanisms (WP 2.5) could contribute to define, from a seismological point of view, the strain field of the region. Our objective is to develop a semi-automatic code able to evaluate the anisotropy of S waves and to apply it to the crustal earthquakes located by WP2.2 for characterizing the deformation and fracture field of the crust. To understand if the anisotropic parameters can change in time and are sensible to variations of stress and/or fluid pressure changes, we want to study anisotropic parameters of repeated earthquakes.

Activities: To estimate the anisotropic parameters in the crust we will investigate shear wave splitting phenomena (the analog of birefringence in optics). We want to develop an automatic analysis code which choose the portion of the signal to be studied staring from the S wave picking and evaluate the anisotropic parameters. Different techniques for the shear wave splitting analysis developed by the different researchers (INGV-RM1, INGV-OV-NA, INGV-CNT, INGV-BO) will be used on a sub- set of events and the results will be compared to define the best method for an automatic evaluation of the anisotropy. Special attention will be done in the analysis of repeated earthquakes, frequents in the area, to understand if temporal variations of anisotropic parameters are detectable. he resulting code will be applied on a large number of earthquake to define the strength and the orientation of the fracture field in the different areas and their relationship with the stress field defined by focal mechanisms, the code will be applied also on the data acquired in Task1 ATF.

Methodologies: Seismic anisotropy is an almost ubiquitous property of the earth, the shear wave splitting is the most unambiguous indicator of anisotropy but the automatic estimation of the splitting parameters presents difficulties because the effect of the anisotropy on the seismogram is a second order effect not very easily detectable. We will compare different codes developed under MatLab which use both covariance matrix decomposition and cross-correlation techniques to estimate the anisotropic parameters of "fast direction" and of "delay time". The resulting code will be applied and automatic evaluation of anisotropy will be computed on the analyzable earthquakes.

Objectives: The relationships between mechanisms/mode of faulting and the seismic release are the basis for the interpretation of the deformation acting in the Messina Strait. Geodetic measurements are a powerful tool that can contribute to clarify many aspects of this issue. In this framework the analysis of triangulation data collected by IGM since 1970 and the analysis of GPS data collected since 1994 will permit an estimates of the strain rates in the Messina Strait and of the interseismic tectonic loading on the fault responsible for the 1908 Messina earthquake

Activities: Since the past century, many good quality geodetic data have been collected and one of the aim of this proposal is the reconstruction and classification of this huge heritge of data. Moreover a new field survey that possibly unify different networks measured in these last years will be planned and realized. Velocity fields and strain-rate patterns will be compared with seismological and geological data available for the investigated area in order to better understand the complex geodynamic setting of this area.

Methodologies: All available data, coming both from periodical and continuous GPS stations will be processed through the GAMIT/GLOBK software packages. We aim to use the horizontal velocities obtained from the combination of permanent and non-permanent GPS data to study the kinematics of the Sicily-Calabria domain. Inter-seismic deformation can be studied from the analysis of surface velocity gradients by adopting relatively simple dislocation models.
Finally we propose a new approach to the models that have been obtained by inversion of leveling data, recorded before and after the earthquake (Lo Perfido, 1909 using a numerical approach, the Finite Element Method (FEM)).

Objectives: The aim of this WP is the analysis of the earthquake focal mechanisms and of the seismogenic stress and seismic strain fields in the Messina Straits area. The analysis will regard both the data coming from the most recent and actual acquisition, and the information collected during the last twenty years by the local and national permanent seismic networks. The new results will lead us to obtain expectably remarkable progresses in the knowledge of tectonic stress accumulation mechanisms and consequent processes of seismogenic faulting in the area of our interest.

Activities: Focal mechanism computation imposes, as preliminary step, accurate enough earthquake locations. The cooperation with the other RUs will allow us to optimize earthquake location information needed for focal mechanism computations. We will use for investigations the recordings by the permanent seismometric networks operating in the region, as well as the recordings from the OBS and on-shore temporary stations installed in the framework of the "Messina 1908-2008" project. The obtained focal solutions will be integrated with the data available in the official databases and in the major literature (Pondrelli et al., 2006, EMMA database), both for critical comparison between results coming from application of different techniques, and for creation of a new FM database with "weighted" data representing un updated catalogue in terms of quantity and quality of solutions reported, particularly in the domain of medium-low magnitudes. The best quality focal mechanisms (errors < 20°) will be used for stress and strain tensor computations through methods widely tested. We expect, in particular, to better delineate the local stress domains detected in the region. Refining of the seismogenic stress model in the Messina Straits area will allow us to obtain useful information about dynamic processes in one of the areas with the highest seismic risk in the Mediterranean region, a piece of knowledge basic for understanding seismic energy accumulation and release mechanisms.

Methodologies: The focal mechanism computation will be performed both by traditional techniques based on use of P-onset polarities (Reasenberg and Oppenheimer, 1985) and by methods based on seismic waveform inversion (Zhu and Helmberger, 1996; Zhu et al., 2006; Dreger and Helmberger, 1993). In particular, the Òcut and pasteÓ method by Zhu and Helmberger (1996) and Zhu et al. (2006) is based on inversion of waveforms recorded by broadband stations. The seismograms are subdivided into Pln and surface wave segments to be inverted for the best moment tensor by a global grid search. Time shifts between synthetics and observations are allowed in order to reduce dependence of the solution on the assumed velocity model and on possible earthquake mislocations. We expect that this method, successfully applied also in the case of earthquakes with magnitude lower than 3 in other regions (Zhu et al., 2006), may furnish good-quality solutions in the Messina Straits area in a magnitude range (2.5-4) non properly represented in the RCMT catalogue and where the solutions estimated from P-onset polarities are often poorly constrained. The focal mechanisms will be used for stress and strain field computations.