INVESTIGATING PULSE-LIKE EARTHQUAKES IN IRANUSING WAVELET TRANSFORM METHOD

The uncertainty in the time history analysis of structure is directly related to the uncertainty inselecting the input acceleration time history for analysis. Therefore, investigating the characteristics ofacceleration time history is of utmost importance. The structure of acceleration time history isinfluenced by various factors, with one of the most important being the site location relative to thecausative fault. Based on the characteristics of earthquakes and their time histories, earthquakes aredivided into two categories: near-field and far-field earthquakes. In locations that are in the near-fieldof the fault, some recorded earthquake time histories contain pulses with long periods and highamplitudes in the velocity mapping, depending on the fault movement mechanism. These pulses havea significant effect on seismic response and structural damage. Based on previous research, pulse-likerecords generally occur due to the phenomenon of directivity rupture of faults and fling effects.Considering this, in areas where pulse-like earthquakes are observed, there is a possibility of therecurrence of such pulse-like events. Therefore, identifying pulse-like earthquakes in different regionsis of great importance for considering special seismic design measures. In this study, the detection ofpulses in large earthquakes in Iran using wavelet transform has been investigated, and as a result,seven earthquakes have been definitively identified as pulse-like. Also, a number of earthquakessuspected to be pulse-like were investigated and analyzed by visual method.

Keywords:

Pulse-Like Ground Motion , Wavelet Analysis , Near-Field Earthquake , Directivity Effects