MAGNITUDE ESTIMATION USING TC-Pd METHOD FOR EARTHQUAKE EARLY WARNING

Abstract

A t, -Pd method for Magnitude estimation for earthquake early warning is tested. The method is based on real-time measurement of period (T.) and peak displacement (Pd) parameters at stations . Here 1726 earthquake records from 105 different earthquake events with magnitude Mw > 5 and epicentral distance < 60 km in Japan (K-net) have been taken for analysis. Ground Motion Period Parameter (tc) and peak vertical displacement (Pd) were calculated for a time window of 3-sec after the P-onset for vertical component of earthquake record. Peak ground velocity (PGV) is calculated for the maximum horizontal ground acceleration for complete time history. A linear regression was developed between M & tc and Pd & PGV. In earlier studies the threshold values are generally set as 1 sec for t,, and 0.5cm for Pd . The recorded values of parameters are compared to the threshold values for issuing alerts. From the results it is found that when T >_ 1 sec then there is a possibility of occurrence of destructive earthquake and if Pd=0.5 cm then PGV was found to be > 18 cm/sec which is also a sign of damaging earthquake. The threshold value for 'r was kept as I sec and for Pd it was kept as 0.5 cm. And threshold for magnitude was kept at Mw 6. By using different statistics for 105 earthquake events it was found that a minimum of 4 stations should exceed threshold of ti 1 sec to issue an warning and minimum I station exceeds a threshold of Pd? 0.5cm to issue an warning.