Fast and accurate determination of earthquake moment, rupture length and stress release for the 2016–2017 Central Italy seismic sequence. Issue 2 (20th February 2019)

• Record Type: Journal Article
• Authors: Nazeri, Sahar; Colombelli, Simona; Zollo, Aldo
• Is Part Of: Geophysical journal international. Volume 217:Issue 2(2019)
• Page Start: 1425
• Page End: 1432
• Publication Date: 2019-02-20
• Subjects: Central Italy -- Seismic sequence -- Earthquake source duration/length -- Earthquake Early Warning parameters -- Seismic moment -- Stress drop; Geophysics -- Periodicals; 550
• DOI: 10.1093/gji/ggz097
• Languages: English
• ISSNs: 0956-540X

Abstract

SUMMARY: In this study, a straightforward and rapid methodology is proposed and tested to determine the seismic moment, the earthquake rupture length/duration and the static stress drop. To this purpose, three ground motion parameters, that is, P -wave peak acceleration (${P_a}$ ), velocity (${P_v}$ ) and displacement (${P_d}$ ) are evaluated as a function of time from the first P arrival. The average of the logarithm of the P -wave amplitude (LPDT curves), corrected for the distance-attenuation effect, is calculated using all the available stations in expanded P -wave time windows. The LPDT curves show an exponential growth shape and increase with time until they reach a constant value (plateau), which is related to the magnitude of the earthquake. From the obtained observations, we demonstrate that the corner time of the plateau level on the weighted-fit curve to the LPDT curves is related to the half-duration of the rupture. Thus, using the theoretical scaling, the source radius and stress drop can be obtained from the measured half-duration of the source. This method has been applied and tested to the records of the 2016–2017 Central Italy seismic sequence, with moment magnitude ranging between 3.4 and 6.5. Our study shows that source parameters match a self-similar, constant-stress-drop scaling with a relatively low average stress drop of about$1.1 \pm 0.5\ \mathrm{ MPa}$, except for the largest event of the sequence showing a relatively higher stress release, which is associated with the dominant radiation from a localized high slip patch on the fracture surface. The proposed approach based on a simple time domain signal analysis is innovative and may complement longer spectral technique for fast estimating earthquake source properties.