Earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records

Abstract

[1] We show that the low-pass filtered, peak amplitudes of initial P-and S-wave seismic signals recorded in the vicinity of an occurring earthquake source correlates with the earthquake magnitude and may be used for real-time estimation of the event size in seismic early warning applications. The earthquake size can be therefore estimated using only a couple of seconds of signal from the P-or S-wave onsets, i.e. while the rupture itself is still propagating and rupture dimension is far from complete. We argue that dynamic stress release and/or slip duration on the fault in the very early stage of seismic fracture, scales both with the observed peak amplitude and with the elastic energy available for fracture propagation. The probability that a fracture grows to a larger size should scale with the energy initially available. Citation: Zollo, A., M. Lancieri, and S. Nielsen (2006), Earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records, Geophys. Res. Lett., 33, L23312,

Evidence for a difference in rupture initiation between small and large earthquakes

“…The ability to correctly distinguish a small shock from a large event through the analysis of the first P-wave observation is crucial for risk mitigation actions triggered by earthquake early warning systems. Several authors demonstrated that the early portion of recorded P-waves contains information regarding the magnitude through its frequency content and/or amplitude [17][18][19][20] . Most of these studies concentrated on the analysis of a fixed P-wave time window (PTW; 3-4 s).…”

The Status of Earthquake Early Warning around the World: An Introductory Overview

“…If four seconds of P-wave data is being used, and the duration of an M 6.5 earthquake is four seconds, can P-wave parameters distinguish an M 7.5 earthquake from an M 6.5 event? There is clear evidence that the amplitude of the P wave within the first few seconds does saturate for M > ~7 earthquakes (Zollo et al 2006;Wurman et al 2007;Murphy and Nielsen 2009;Brown et al 2009, this issue). To try to reduce this problem, several methodologies use longer time windows of the P wave and/or the S wave to update magnitude estimates (Zollo et al 2006;Kamigaichi et al 2009, this issue).…”

“…There is clear evidence that the amplitude of the P wave within the first few seconds does saturate for M > ~7 earthquakes (Zollo et al 2006;Wurman et al 2007;Murphy and Nielsen 2009;Brown et al 2009, this issue). To try to reduce this problem, several methodologies use longer time windows of the P wave and/or the S wave to update magnitude estimates (Zollo et al 2006;Kamigaichi et al 2009, this issue). When using the frequency content of the P wave there is less empirical evidence for saturation (Kanamori 2005;Olson and Allen 2005;Lewis and BenZion 2008;Brown et al 2009, this issue), although this conclusion is controversial (Rydelek and Horiuchi 2006;Yamada and Ide 2008), and a satisfactory physical explanation remains elusive.…”

“…The use of the peak displacement, velocity, or acceleration of the first few seconds, typically three seconds, of the P wave has been shown to scale with magnitude (Wu and Kanamori 2005b;Zollo et al 2006;Wu and Kanamori 2008a) and ground motion Wu and Kanamori 2005a). The peak displacement, referred to as P d , is usually found to be the most robust amplitude parameter provided that integration or double integration of the waveform at a station is possible.…”

Rapid Estimation of Earthquake Source and Ground-Motion Parameters for Earthquake Early Warning Using Data from a Single Three-Component Broadband or Strong-Motion Sensor

“…These algorithms require the seismic waveforms either from a single seismic sensor (the so-called on-site warning systems; e.g., Wu and Kanamori, 2005;Kanamori, 2005;Zollo et al, 2006;Böse et al, 2007) or from a seismic network or subnetwork (the so-called regional warning systems; e.g., Wu and Teng, 2002;Allen and Kanamori, 2003;Cua and Heaton, 2007). On-site and regional warning approaches deliver estimates of source and ground-motion parameters with different speed and accuracy (e.g., Kanamori, 2005).…”