2. Earthquake recording, seismicity and seismotectonics
With a history stretching back over 5,000 years, China is one of the world’s oldest civilizations, with which only a few countries on the planet can compete for longevity. The first ever historical record of an earthquake was carved into bamboo in Shandong province, eastern China in 1831 BC. Large numbers of epitaphs throughout Chinese history document evidence of past earthquakes, and the processes underpinning such earthquakes have always fascinated the Chinese. The theory of “Yin” and “Yang” was considered as a possible explanation, and even Chinese royalty was inspired to try and understand the seismic phenomenon, with the Emperor Kangxi (1654-1722) attempting to describe the spatial distribution of earthquakes in China in an article written in 1720.

The seismoscope, the first instrument designed to detect earthquakes (figure 1), was invented by a Chinese, named Zhang Heng, in 132 AD, a full 1700 years before Europeans would conceive of such an invention.

Figure 1. The first seismoscope invented by Zhang Heng in 132 AD. Earthquake records in China stretch
back for over 3000 years. Chinese scientists obtain the intensity of a documented earthquake by relating
written accounts of effects and damage to an intensity scale that is similar to the Modified Mercalli Scale.

Records of past earthquakes in China have been collated in various catalogues over the past 50 years. In the 1950s eight thousand historical references were inspected, from 1189 BC, and more than 15,000 accounts of earthquakes found. The results were published in Chronological tabulation of Chinese earthquake records (Lee, 1957).

The earthquake records were updated 26 years later and published in The Catalogues of Earthquakes in China (1831 BC -1969 AD) (Gu, 1983a). Earthquake data for the 1970s were soon subsequently published in the The Catalogues of Earthquakes in China (1970 -1979 AD) (Gu, 1983b).

With such a large, historic earthquake catalogue, scientists are able to estimate the return periods of even the largest magnitude earthquakes and – aided by an appreciation of the tectonic setting of China and its neighbours - seek to understand the pattern of earthquake occurrence through time.

Figure 2. Major tectonic movements and faults of China and its surroundings (after Ma, 1987).

Mainland China is located in the southeastern part of the Eurasian tectonic plate which is bordered by four other plates including the Indian Plate and the Philippine Sea plate (figure 2). The subduction of the Philippine Sea plate beneath Eurasia has resulted in an area of large scale interplate earthquakes that affect the offshore island of Taiwan.

Intraplate earthquake epicentres throughout China (figure 3) are primarily located near known faults that have arisen due to the collision between the Indian and Eurasian plates. The subsequent rise of the Tibetan plateau and resistance to movement by stable, inactive tectonic blocks causes a large build up of stress and hence extensive strike-slip and thrust faulting in western China.

Figure 3. Earthquake epicentral map of China (Ms 6.0 780 BC – 1994 AD) (after RGCERP, 1995)

There are six times more intraplate earthquakes in western China than in the east (Fu, 2000). Earthquakes in the east, however, have resulted in the largest economic losses mainly because of the higher population densities. Within the last 500 years devastating earthquakes have occurred throughout China resulting in severe damage and great loss of life, and a selection are briefly addressed in the following sections.

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