![]() Innovatively, we use the estimates of E r and M 0 (i.e., through the slowness parameter 23) to introduce a rapid response magnitude (M r). Then, the procedure is applied to about 775 earthquakes of the 2016–2017 Central Italy sequence 22 with M w in the range 2.5–6.5. We first calibrate empirical attenuation relationships between the integral of squared velocity (IV2 S) and the peak displacement (PD S) with respect to E r and M 0, respectively, considering 229 earthquakes ranging from M w 2.4 to 6.1, mostly belonging to the L’Aquila (2009) seismic sequence 21. The methodology is applied to Central Italy, used as an example region where the seismic hazard for residential buildings is dominated by close-distance earthquakes of low-to-moderate magnitude 20 (i.e., from 4.5 to 6.5). In this study, we present a new procedure to measure the earthquake size using rapid assessments of both E r and M 0, considering S-wave recordings within 100 km from the epicenter. Although automatic procedures for the rapid estimation of M e using P-wave recordings have been proposed both at teleseismic 18 and local 19 distances, a strategy to combine the information provided by M w and M e for a rapid assessment of the damage potential of an earthquake has not been proposed yet. Indeed, high energy-to-moment ratios indicate that the intensity of radiated energy at high frequencies is large relative to the size (measured by moment) of an earthquake, with significant implications on hazard assessment 17. Since M e is directly linked to the source dynamics, it is more sensitive to high-frequency source details such as variations of the slip and/or stress conditions, and the dynamic friction at the fault surface during the rupture process. Using teleseismic broadband P-wave recordings, a magnitude scale (M e) was introduced 15 based on measurements of the radiated energy (E r) and revising the Gutenberg and Richter relationship 16 between E r and the surface-wave magnitude M s. For example, M w can be complemented with a magnitude scale based on the high-frequency level of the Fourier spectrum 14. ![]() Since different magnitude scales provide different information about the static and dynamic features of the earthquake rupture, magnitudes other than M w could better characterize the earthquake size in terms of high-frequency energy release 11, 12, 13. Moreover, recent studies 8, 9, 10 showed that the Δσ variability is a key parameter for explaining the between-event residuals at short periods. For example, earthquakes with similar M w but different stress drop (Δσ) can generate different ground motion levels 7, suggesting that a rapid assessment of Δσ could allow more reliable predictions of the earthquake-induced ground motion severity to engineering structures (hereinafter, shaking potential). Since M w is based on an estimate of the seismic moment M 0 4, 5, it provides fault-averaged, low-frequency information on source processes but relatively less information about the small-wavelength high-frequency rupture details 6. The moment magnitude M w 2, 3 is used by the seismological community as the primary measure of the earthquake size. To improve the spatial resolution of such maps for rapid response actions, the rapid determination of an earthquake size and location supports the information provided by the actual ground motion measurements (if available) and predicted ones. In this context, shaking maps 1 become a de-facto standard for a timely dissemination of the ground shaking experienced in the area struck by an earthquake. In the aftermath of an earthquake, the rapid assessment of both location and extension of potentially damaging ground shaking is a primary task for seismological agencies supporting emergency managers. The procedure we propose is therefore a significant step towards a quick assessment of earthquakes damage potential and timely implementation of emergency plans. ![]() The new M r scale allows us to improve the prediction of the earthquake shaking potential, as shown by the reduction of the between-event residuals computed for the peak ground velocity. Since the observed seismicity does not agree with the assumptions on stress drop in the definition of M w, we exploit the availability of both E r and M 0 to modify the definition of M w and introduce a rapid response magnitude (M r), which accounts for the dynamic properties of rupture. Our results show the limitation of using M 0, and in turn M w, to capture the variability of the high frequency ground motion. ![]() The analysis of the M 0-to-E r scaling highlights a breaking of the source self-similarity, with higher stress drops for larger events. In this work the scaling of seismic moment (M 0) and radiated energy (E r) is investigated for almost 800 earthquakes of the 2016–17 Amatrice-Norcia sequences in Italy, ranging in moment magnitude (M w) from 2.5 to 6.5. ![]()
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