Rapid estimation of the probability of seismic intensity for affected counties based on attenuation relationship

Shaking intensity distribution immediately following an earthquake is valuable for emergency response. Such intensity distribution is usually derived from empirical relationship between seismic intensity and ground motion parameters. If there is a seismic station at the site, the ground motion parameter is quantified by the station record; if there is no seismic station, the ground motion parameter is just estimated from attenuation relationship. Due to the sparse seismic station coverage and the difficulty in real-time data acquisition in China, the rapid results of ground motion parameter, which will be changed into shaking intensity later according to empirical relationship between seismic intensity and ground motion parameter, are just estimated from attenuation relationship. However, there is uncertainty in attenuation relationship itself, the estimated ground motion parameter is dubious and is not suitable to be used for the output of the deterministic shaking intensity distribution. Therefore, we propose a method to compute the probability of shaking intensity for counties in seismic area by means of the stochastic variable ε in attenuation relationship. Specifically, we build the logarithmic normal distribution about peak ground acceleration, using the estimated value and the standard deviation of the attenuation relationship, to calculate the probability of every possible shaking intensity and the probability exceeding seismic fortification intensity for counties in seismic area. Then, the March 8 1966 Xingtai M_S6.8 earthquake is taken for example to show the feasibility of this method. It is thought that the intensity displayed in a probability way is more reasonable than before. So, it is recommended that the intensity characterized by probability should be considered in emergency response and rapid earthquake damage assessment.