Resumen de Rapid estimation of earthquake magnitude by a new wavelet‐based proxy
Sanam Atefi, Reza Heidari, Noorbakhsh Mirzaei, Hamid Reza Siahkoohi
Quick and correct estimation of earthquake magnitude, within the first few seconds after P‐wave arrival and before the arrival of damaging strong ground motions, is considered to be the main challenge in earthquake early warning systems (EEWSs). In recent years, three frequency‐based approaches, predominant period ( τmaxPτPmax ), characteristic period ( τcτc ), and log‐average period ( τlogτlog ), have been applied by EEWSs or studied by scientists to estimate earthquake size. τmaxPτPmax and τcτc parameters suffer from biasing toward high frequencies, which yields erroneous results. For magnitude prediction in EEWSs, we propose a new wavelet‐based scale λlog λlog obtained from P‐wave time windows of borehole accelerograms of earthquakes in Japan with magnitudes of MJMAMJMA 3–8 and epicentral distances less than 100 km. For events with MJMA≥5.5MJMA≥5.5 , the new empirical formula obtained from regression of log(λlog)−MJMAlog(λlog)−MJMA provides more accurate and reliable magnitude estimation than the other τmaxPτPmax , τcτc , and τlogτlog proxies. The magnitude estimation error—one of the main causes of false and missed alarms in EEWSs—can be reduced using λlogλlog parameter.
