Moment Magnitude (M_w) Estimation of Weak Seismicity in Northeastern Italy

Fast MW estimation of microearthquakes recorded around the underground gas storage in the Montello-Collalto area (Southeastern Alps, Italy)

“…where a quantifies the magnitude scaling factor, D(r, r ref , f) represents the propagation term as a function of the hypocentral distance (r) and c T is a constant defined specifically for the response spectra computed at various periods (f = 1/T). Moratto et al (2017) estimated the scaling factor a equal to 1.49, observing that it is similar to the typical scaling of 3/2 (or reciprocally its inverse 2/3) between M W and M L . It has actually been demonstrated that the scaling coefficient between log (SA) and M W is exactly 2/3, the principal reason being the anelastic attenuation, i.e., the same explanation for the 3/2 scaling between M L and M W observed for small earthquakes (Deichmann 2017;Moratto et al 2017).…”

“…Moratto et al (2017) estimated the scaling factor a equal to 1.49, observing that it is similar to the typical scaling of 3/2 (or reciprocally its inverse 2/3) between M W and M L . It has actually been demonstrated that the scaling coefficient between log (SA) and M W is exactly 2/3, the principal reason being the anelastic attenuation, i.e., the same explanation for the 3/2 scaling between M L and M W observed for small earthquakes (Deichmann 2017;Moratto et al 2017). In particular, the amplitude value of the response spectrum at a particular period is equivalent to measuring the maximum amplitude of a seismogram filtered with a narrow second-order pass-band filter with a certain amount of damping, independently of the seismic moment.…”

“…Moreover, the response spectra at 0.3 and 1.0 s are widely used engineering parameters that are often available in real time (e.g., ShakeMap parameters) and thus can be used to provide rapid estimates of M W . Moratto et al (2017) applied this method to the weak seismicity recorded in Northeastern Italy and observed underestimation of M L with respect to M W for earthquakes with M W < 1.5. Similar results were obtained by Moratto et al (2019), who inverted the full source spectra to estimate the seismic moment and the corner frequency for a selection of 30 well-located earthquakes with 1.0 ≤ M L ≤ 3.0 occurred in a restricted area of Northeastern Italy.…”

“…In this work, we use and extend the method originally proposed by Atkinson et al (2014) and applied by Moratto et al (2017) to Northeastern Italy at regional scale, to estimate the moment magnitude of the microseismicity recorded by the RSC in the period 1 January 2012-31 July 2018. The ultimate goal is to have a robust and fast procedure for the quasi real-time estimation of M W using the response spectra even for very small earthquakes.…”

Application of monitoring guidelines to induced seismicity in Italy

“…Moment magnitude M W is only provided a few hours after the event, as additional information, when the seismic moment tensor is available for events of particular interest, but not for smaller events (the size of weak seismic events in Italian volcanic areas is sometimes quantified using yet another magnitude scale based on duration, M D ). In a rather promising alternate approach, Atkinson et al (2014) proposed the computation of M w for weak local events based on the use of response spectra; a formulation that has later been applied to the weak seismicity of North-East Italy by Moratto et al (2017). All these magnitude types (i.e.…”