Publication Date:
2017-04-04
Description:
It has been shown that the initial portion of P and S wave signals can provide
information about the final earthquake magnitude in a wide magnitude range. This
observation opens the perspective for the real-time determination of source parameters. In
this paper we describe a probabilistic evolutionary approach for the real-time magnitude
estimation which can have a potential use in earthquake early warning. The technique
is based on empirical prediction laws correlating the low-frequency peak ground
displacement measured in a few seconds after the P and/or S phase arrival and the final
event magnitude. The evidence for such a correlation has been found through the analysis
of 256 shallow crustal events in the magnitude range Mjma 4–7.1 located over the entire
Japanese archipelago. The peak displacement measured in a 2-s window from the
first P phase arrival correlates with magnitude in the range M = [4–6.5]. While a possible
saturation effect above M ’ 6.5 is observed, it is less evident in an enlarged window of 4 s.
The scaling of S peaks with magnitude is instead also observed at smaller time lapses
(i.e., 1 s) after the first S arrival. The different scaling of P and S peaks with magnitude
when measured in a 2-s window is explained in terms of different imaged rupture surface
by the early portion of the body wave signals. We developed a technique to estimate
the probability density function (PDF) of magnitude, at each time step after the event
origin. The predicted magnitude value corresponds to the maximum of PDF, while its
uncertainty is given by the 95% confidence bound. The method has been applied to the
2007 (Mjma = 6.9) Noto Hanto and 1995 (Mjma = 7.3) Kobe earthquakes. The results of
this study can be summarized as follows: (1) The probabilistic algorithm founded on
the predictive model of peak displacement versus final magnitude is able to provide a fast
and robust estimation of the final magnitude. (2) The information available after a few
seconds from the first detection of the P phase at the network can be used to predict the
peak ground motion at a given regional target with uncertainties which are comparable to
those derived from the attenuation law. (3) The near-source S phase data can be used
jointly with P data for regional early warning purposes, thus increasing the accuracy and
reliability of magnitude estimation.
Description:
Published
Description:
B12302
Description:
4.1. Metodologie sismologiche per l'ingegneria sismica
Description:
JCR Journal
Description:
reserved
Keywords:
Bayesian approach
;
P and S wave
;
04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
