RISK ASSESSMENT OF EARHQUAKES, TSUNAMIS AND OTHER DISASTERS IN CHINA AND TAIWAN

ISSN 8755-6839 SCIENCE OF TSUNAMI HAZARDS Journal of Tsunami Society International Volume 40 Number 4 2021 RISK ASSESSMENT OF EARHQUAKES, TSUNAMIS AND OTHER DISASTERS IN CHINA AND TAIWAN George Pararas-Carayannis Tsunami Society International ABSTRACT The historical record indicates that China's extensive east coast and the rim of the CrossStraits region bordering Taiwan, are vulnerable to the destructive impact of major weatherrelated disasters, as well to major catastrophes by earthquakes and tsunamis. The provinces of Shanghai, Guangdong, Fujian, and Zhejiang in China, as well as the neighoring Taiwan, are particularly threatened. Mitigating the impact of future disasters in this region requires an integrated multi-disciplinary planning approach which entails, first identifying the disasters, then assessing their individual impacts, defining geographical limits of vulnerabilities, predicting recurrence frequencies, developing possible scenarios of future socio-economic impacts, resolving Land Use conflicts of vulnerable areas and, finally, preparing a comprehensive plan for preparedness. This present study reviews, assesses and analyzes potential disasters of such multiple types of diasters in China, with particular emphasis on earthquakes and tsunamis along the Cross-Straits region bordering with Taiwan, and further North to the Bohai Bay region, bordering with North Korea. Furthermore, the present study outlines sustainable, adaptive measures and strategies that must be implemented to help minimize potential future losses of lives and damage to property in these regions from such disasters. Finally, the study proposes guidelines for the preparation of a comprehensive disaster plan for China, the Cross-Straits region and further North – a plan which should be implemented or expanded in order to mitigate future adverse impacts on human lives and significant economic resources. Vol. 40, No. 4, page 315 (2021) 1. INTRODUCTION China and Taiwan are vulnerable to multiple types of natural disasters, including weather-related and of major earthquakes and tsunamis. The regional vulnerability to earthquakes and tsunamis is particularly high because of the long coastlines and proximity to many inland and coastal faults. China’s coastline extends for 1800 km from its border with Korea in the north to its border with Vietnam in the south, and includes about 6,500 coastal islands. China’s eight provinces, which includes two mega cities, several medium and small-sized cities, and one autonomous region, border this extensive coastline. More than 40 percent of the population, or about 500 million people live in coastal areas - a trend which continues to rise at a high rate. Critical infrastructure facilities have been built in potentially vulnerable regions with inadequate risk assessment of the need for more stringent engineering guidelines for both static and dynamic stabilities from the impact of future extreme disaster events such as storms, landslides, earthquakes or tsunamis. The present analysis provides a background of the tectonic evolution of both China and Taiwan, a brief overview of historical data, discusses some of the major past earthquakes, tsunamis, typhoons, storm surges and landslides, and outlines regional and local vulnerabilities, particularly in the higher populated Cross-Straits region (Fig. 1). . Fig. 1. China / Cross-Straits Region In order to illustrate future challenges in mitigating the potential impact that disasters can have, the study summarizes the geological and geophysical characteristics of the two prominent seismic zones that can produce destructive earthquakes and tsunamis - the Fuzian Province's seismic zone along the western side of the Cross-Straits, and Taiwan's seismic zone of active subduction and collision. Additionally, the present analysis provides Vol. 40, No. 4, page 316 (2021) a brief overview of recent typhoon disasters, scenarios of potential future events, and dynamic mechanisms that can produce flooding of low-lying areas from storm surges and tsunamis. Finally, the overview explains some of the maximum probable events which engineers and planners may face in the future, and summarizes the approach that must be taken to develop the necessary criteria for proper land use, adequate building codes, engineering guidelines, and finally recommends strategies that can be adopted to mitigate the future impact of different disasters in order to achieve the sustainable development of coastal cities along the Cross-Straits region and further North to China’s Bohai Bay. 2. SEISMOTECTONICS OF CHINA AND OF THE CROSS-STRAITS REGION The following overview of the seismotectonics of China's Central and Coastal regions provides background information on the complex, long term, geodynamic development of the Cross-Straits region and the potential for destructive earthquakes, tsunamis and other collateral hazards along China’s extensive coastalines. 2.1 China's Seismotectonic Evolution Before the Paleozoic Era, the Eurasian tectonic plate mainly controlled China's geological activity. However, in the middle of the Cenozoic Era, the activity was affected mainly by the interactions of the Pacific and Indian plates (Hellinger et al, 1985). The high seismicity of central and eastern Asia resulted from the northward collisional convergence (at 50 mm/y) of the India tectonic plate against the Eurasian plate (See Fig. 2). Fig 2. Uplift of the Himalayas, and of the Qinghai - Tibet Plateau Vol. 40, No. 4, page 317 (2021) This tectonic convergence - which begun about 55 million years ago - uplifted the Asian highlands and resulted in the growth of the world's largest orogenic belt, the Himalayas, and the associated Qinghai - Tibet Plateau, which has an average elevation of over 16,000 feet - the highest and largest plateau on Earth (See Fig. 2). The active collision is the continuing cause of frequent large earthquakes between India and Tibet and throughout the surrounding areas. As the India plate kept on moving northward and intruding into Asia by as much as 1,200 kms, regions north of the Himalayas moved laterally to the east and southeast along large strike slip faults such as the Altyn Tagh, pushing into central China and furthermore resulting in extrusion and crustal movement. As the collision continued, there were hundreds of kilometers of crustal block displacement to the east and to the southeast in the direction of China. China’s overall seismicity is the result of such collision during the earliest Eocene (~50 Ma) (Ye et al. 1985). Figure 3 illustrates the source mechanisms of earthquakes in the Qinghai - Tibet plateau region and the extension that takes place to the southeast and to the east in the direction of China. Also, the early seismotectonic evolution is characterized by the merger of several micro-continents throughout the entire Phanerozoic (Zhang et al., 1984; Hendrix and Davis, 2001). Fig. 3. Interpretation of source mech (...truncated)