Intensity distribution from the 1918 Mw 7.3 Shantou, China, Earthquake

The Pearl River Delta (PRD) region of Guangdong Province is one of the most prosperous regions in China. Although PRD is in an area of low-to-medium seismic activity, many factors such as high economic exposure, dense population, and site effects may exacerbate the earthquake risk in the region. To assess the earthquake hazard and risks in this region, the 1918 Shantou earthquake of magnitude 7.3, the largest recorded earthquake near the PRD region, is studied. Two hundred forty-one macroseismic intensity reports from this earthquake are collected and assigned MMI values. The locations, where available, are determined to estimate the impact of ground motion. The distribution of the MMI value is then plotted in a map, and the attenuation of intensity values with distance is compared with the attenuation relationships developed by Atkinson and Wald (2007) and Jia (1996). The MMI range of macroseismic report is from IV to X, and the earthquake was felt 1,000 km away. For the PRD region, the MMI value of macroseismic report ranges from V to IV. The inferred intensity data from macroseismic reports fit well with the Xiamen Bridge curve from Jia (1996), which validates the method of assigning MMI value and location to each intensity report. Macroseismic data can be used as an alternative to characterize shaking intensities from historical earthquakes when the instrumental data is limited.