Seismic intensity provides useful information on the regional distribution of earthquake effects and has been used to assess seismic hazards and damages. The concept of intensity has been considered as a method to classify severity of the ground motion on the basis of observed effects in the stricken area. In 1996, the Japan Meteorological Agency (JMA) developed a new seismic intensity measurement scale using three‐component strong ground motion records in order to provide a measure of the strength of the seismic motion, which is compatible with the existing JMA intensity scale. By applying a band‐pass filter to the frequency domain and a vectoral composition of the three components in the time domain, the JMA seismic intensity scale (I JMA ) can be calculated without subjective judgement. In this study, we apply the I JMA method to the acceleration records of three recent significant earthquakes in California. For a Modified Mercalli Intensity (MMI) between IV and VIII, a new relation between MMI and log a 0 , obtained in the process of calculating the new I JMA , is given by the equation MMI=3.93 log a 0 −1.17. We propose this relation as a new instrumental seismic intensity (I MM ) compatible with the California region MMI.
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Shabestarı et al. (2001) studied this question.