A Method to Extract Earthquake Motions Accurately from Continuous Records Observed in a Noisy Area

Abstract

We proposed a method to extract earthquake motions accurately from continuous observation records in noisy places. A simple method to connect the extracted records with data of an earthquake catalog was also proposed. We installed 4 accelerometers in a downtown area of Tokyo. Earthquake motions were picked based on the Fourier amplitude in the range from 0.5 to 2.0 Hz in which the amplitude level of microtremors was small. This method resulted in higher accuracy rate and higher extraction rate than the general method using STA/LTA. Although this method is difficult to extract for earthquakes smaller than M3, we successfully extracted 120 earthquakes including the earthquake occurred overseas from records of about half a year even in the noisy downtown area of Tokyo.