A Proposed Method for Instrumental Intensity Determination in West China Using Modified Spectrum Intensity

Acceleration records and their corresponding intensity materials of recent destructive earthquakes in West China were collected in this article.The relativity between various strong ground motion indices and intensity was compared with a method based on hypothesis testing,which indicated that spectral intensity with 20% damping ratio(SI0.2) was the index that most significantly related to intensity.As an improvement,SI0.2 was modified depending on the predominant period of spectral acceleration and the site condition of the station.The instrumental intensity determined by modified SI0.2 was identical with the actual intensity for 70 percents of the stations,which indicated that modified SI0.2 was efficient and reliable in instrumental intensity determination.So modified SI0.2 defined in this article was proposed to determine the instrumental intensity for destructive earthquakes in West China.