## 1 Introduction
Comparisons of the theoretical site response from 2D arrays with empirical ones from earthquake recordings at seismic stations indicate that 2D array seismic noise methods allow the estimation of the most relevant and reliable information about the local S-wave structure for site response. Amongst these studies in recent years, the use of micro-seismic arrays for seismic noise recordings have proved to provide vital information for rapid and cost-effective microzonations of urban areas (among the others [7-9]). Until now, a crucial point limiting the applicability of these array measurements in urban area is that expensive, heavy and stand alone stations to be deployed in the field are required, especially when techniques aimed at resolving the subsoil three dimensional, 3D, structure [10] are applied. This of course limits the number of stations that can be used simultaneously, therefore limiting the success of the experiments. Techniques have been developed to overstep this drawback, but very often they require both strong assumptions on the wavefield's nature and the usage of array geometries that are difficult to implement in urban areas. Moreover, standard arrays are deployed using stand-alone stations that do not allow a fast check of the data quality in the field, limiting the potential application of the data acquisition. A promising solution to these issues is provided by the rapid improvement in telemetry and computer technology, which is literally driving a revolution in seismology and earthquake engineering. The earliest application of wireless communication technology started in the late 90s [11], when wireless sensors were connected together with embedded PC for structural monitoring purposes. These earlier applications first showed that real-time processing of data can be performed locally, and that wireless monitoring systems are feasible, reliable and cost effective. Over the last few years, prototype structural wireless monitoring systems have been validated by tests performed on bridges and other structures [12], where they have been found to be highly cost-competitive, completely autonomous and very reliable alternatives to traditional wired systems. Recently, [PERSON] _et al_. [13] firstly proposed to use a wireless mobile ad-hoc network of standard seismological stations equipped with high sensitivity, but also highly expensive, Earth Data digitizers for site-effect estimate applications. The system allows for the retrieval of data in real time, and thus, to undertake preliminary in-field data processing. To overcome the resolution problem posed by a reduced number of stations available, the authors proposed to repeat the measurements using consecutive arrays with different sizes. At the present time, the _Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum_ (GFZ-Potsdam) and the _Humboldt University of Berlin_ (HU-Berlin) are developing an innovative, self-organizing wireless mesh information network made up of low-cost sensing units equipped with Micro Electro Mechanical Systems (MEMS) accelerometers, with the aim of setting up earthquake early warning systems for mega cities [14,15]. This innovative system, named the Self-Organizing Seismic Early Warning Information Network (SOSEWIN) was developed within the framework of the European projects SAFER (Seismic eArly warning For EuRope, [[http://www.saferproject.net](http://www.saferproject.net)]([http://www.saferproject.net](http://www.saferproject.net))) and EDIM (Earthquake Disaster Information systems for the Marmara Sea region, Turkey, [[http://www.cedim.de/EDIM.php](http://www.cedim.de/EDIM.php)]([http://www.cedim.de/EDIM.php](http://www.cedim.de/EDIM.php))), and a first test version has been deployed since July, 2008, in Istanbul, Turkey.