Abstract:Peak ground acceleration (PGA) in the near field is associated with earthquake damage, but practical instances of the impact of PGA distribution in the near field of different types of focal mechanism is rarely reported.Using the intensive digital seismic records of the capital circle strong motion network, this paper studies two earthquakes that occurred in April 2003 with an epicenter located in Tangshan.Using data from the strong motion network and the temporary seismic network in Sichuan, Gansu, and Shanxi, it also studies two earthquakes that occurred in July and August 2008 with an epicenter located in Wenchan.By using a function of the thematic map in ArcGIS software, the distribution of both the horizontal synthesis and vertical PGA is established, obtaining the differences in earthquake PGA distribution in the near field from the faults and strike-slip faults, and the thrust and strike-slip faults.In this paper, we study the impact of different focal mechanisms in the Ninghe and the Wenchuan earthquake on PGA;the difference in the influence of various focal mechanisms to PGA is especially striking.The results show that this difference is prominent, and that the distribution of major earthquakes PGA is complex in the near field, while that of medium-small earthquakes is also complex.The most crucial place for death and destruction is in the near field.Spectrum analysis established that there are differences in the lower frequencies of seismic waves.Now that there are more buildings and that a greater proportion are multistory and large, the self-vibration period is longer.High values in PGA of nearly vertical strike-slip earthquakes are symmetrically distributed along the fault, while normal faults and reverse faults are concentrated in the hanging wall.The distribution of PGA is complex in the near field, and it is worth noting that the phenomenon of low frequency dip-lip earthquakes is crucial to the input of power and materials in emergency rescue following destructive earthquakes.
