AGU Fall Meeting, San Francisco, USA, 14-18 December, 2009
A. Zollo, O. Amoroso, M. Lancieri, 1, Y. Wu, H. Kanamori
Most of worldwide developed Earthquake Early Warning Systems (EEWS) are conceived as either “regional” (network-based) or “on-site” (stand-alone) systems (Kanamori,2005). A “regional” EEWS is based on a dense sensor network covering a portion or the entirety of an area that is threatened by earthquakes. The relevant source parameters (event location and magnitude) are estimated from the early portion of recorded signals and are used to predict, with a quantified confidence, a ground motion intensity measure at a distant site where a target structure of interest is located. An “on-site” EEWS consists of a single sensor or an array of sensors deployed in the proximity of the target structure that is to be alerted, and whose measurements of peak amplitude and/or predominant period on the initial P-wave motion are used to predict the ensuing peak ground motion (mainly related to the arrival of S and surface waves) at the same site. Wu and Kanamori (2005,2008) have proposed a methodology for on-site early warning applications aimed at the rapid assessment of earthquake damage potential, which is based on the near source (epicentral distance smaller than 30 km), real-time measurement of the peak displacement (Pd) and a period parameter(tc) from early P-wave signals.
In this note we explore the feasibility of applying a similar approach in Italy, based on the analysis of the strong motion records from the European Strong Motion Data Base and from the main events (M=3.4) of the recent 2009, Mw 6.3 Central Italy (L’Aquila) earthquake sequence. The empirical relationships for early warning parameters (PGV,peak ground velocity, vs Pd and tc vs Magnitude) are compared with measurements on Japan and Taiwan earthquakes in a wide distance/magnitude range. By extending the observation distance to 100 km, and by comparing data from different worldwide seismic regions, we generalize the Wu and Kanamori’ method by proposing an integrated regional/on-site early warning method which can be used in the very first seconds after a moderate to large earthquake to map the most probable damaged zones. The settings of specific thresholds for Pd and tc allows to rapidly issue an earthquake alert based on a four entries, decision-table scheme. The proposed approach is suitable for Italy, where, during the last two decades, a dense network of wide dynamic-range accelerometer arrays has been deployed by the Department of Civil Protection, INGV and other regional research agencies.