Earthquake Hazards and Large Dams in Western China A Probe International Study By JOHN JACKSON April 2012 PROBE INTERNATIONAL EDITOR: PATRICIA ADAMS John Jackson is a pseudonym for a geologist with detailed knowledge of western China who wishes to remain anonymous to protect his sources. TABLE OF CONTENTS EXECUTIVE SUMMARY Page 1 INTRODUCTION Page 2 ANALYSIS Page 3 DISCUSSION Page 4 CONCLUSION Page 10 ENDNOTES Page 11 RESOURCES Page 14 APPENDIX A Page 16 − TABLE 1: Summary of ziyuan_b dam database for Page 16 selected rivers in western China − TABLE 2: Summary of U.S. Geological Survey Page 17 (USGS) earthquake database, 1973 – 2011 − TABLE 3: Percentage of total dams in each seismic Page 18 hazard zone for selected rivers in western China − TABLE 4: Percentage of total megawatt (MW) Page 19 capacity in each seismic hazard zone for each river − TABLE 5: Estimated number of dams completed and under construction before 2004, as of 2011, and the Page 20 percentage increase − TABLE 6: Incidences of RIS resulting in damage to dams and other structures, 1937 – 1981 Page 21 APPENDIX B Page 22 − FIGURE 1: Seismic hazard map showing dams Page 22 and major earthquake epicenters in western China Page 23 − FIGURE 2: Map of major dams in China (map "ziyuan_b") Page 24 − FIGURE 3: Geological Map of Nujiang, Lancang, and Jinsha River area Page 25 − FIGURE 4: Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements Page 26 − FIGURE 5: Proximity of large dams to seismic hazard zones and shallow (< 10 km) earthquakes in western China 0 Executive Summary By constructing more than 130 large dams in a region of known high seismicity, China is embarking on a major experiment with potentially disastrous consequences for its economy and its citizens. A comparison of large dam 1 locations and seismic hazard zones for dams that are built, under construction, or proposed for the Tsangpo, Po, Salween (known as Nu in China), Mekong (Lancang in China), Yangtze, Yalong, Dadu, Min, and Yellow river headwaters in western China, indicates that 48.2 percent are located in zones of high to very high seismic hazard. The By constructing remaining 50.4 percent are located in zones of moderate more than 130 seismic hazard, and only 1.4 percent are located in zones of low seismic hazard (see Table 3). With respect to power large dams in a generation capacity, 67.2 percent of the combined total region of known megawatt capacity is located in high to very high seismic high seismicity, hazard zones, 32.5 percent in zones of moderate seismic China is hazard, and only 0.3 percent in zones of low seismic hazard embarking on a (see Table 4). major experiment Moreover, the rapid rate of construction and the location of with potentially dams around clusters of M>4.9 earthquake epicenters (of disastrous events between 1973 and 20112) is significant cause for consequences for concern. In less than a decade there has been a 267 percent its economy and increase in dams built and dams under construction. The its citizens. risk of earthquake damage caused by the region’s high natural seismicity is compounded by the risk of Reservoir- 3 Induced Seismicity (RIS), which results from the seasonal discharge of water from the region’s reservoirs. The risk of earthquake damage to dams is also compounded by the increased risk of multiple dam failures due to the cascade nature of dam spacing.4 The purpose of this report is to highlight for the Chinese government the urgent need for an independent, comprehensive, and expert seismic risk assessment of the extensive dam-building program underway in western China. In order to provide the best assessment of the seismic risk hazard of China’s dam-building program, the recommended study should be prepared using mapping software similar to that used in this report but with an up- to-date list of dams with precise latitude and longitude locations, and size of dams situated within the known 1 seismic hazard zones and in relation to historical temblors of more than M4.9. The proposed study would inform risk assessments and investment decisions, highlight the need for improved safety standards in dam construction and operation, as well as better emergency preparedness, and lead to the cancellation of dams which pose an unacceptable risk to public safety.5 The proposed study must also be disclosed to China’s citizens, press, power companies, financial institutions, and law-makers to ensure an informed public debate is undertaken on the risks of dam-building, as well as to ensure liability for hazards and damages is properly The purpose of assigned, and safety standards and emergency preparedness this report is to procedures are widely disseminated and debated. Due to the rapid rate of dam construction in China, this proposed highlight for the study should be completed as soon as possible. Chinese government the The database of dams built, under construction, and urgent need for planned for China’s rivers, used by this study, comes from an independent, a map prepared by HydroChina prior to 2004, with data comprehensive, confirmed by more recent surveys, as well as Google Earth satellite images. Based on this review, it appears that about and expert half of these dams have not yet been built, but that the pace seismic risk of construction is rapid.6 This makes a seismic risk hazard assessment of the assessment of dams in western China all the more urgent. extensive dam- building program Introduction underway in Figure 1 shows the locations of major dams either built, western China. under construction, or proposed for the Tsangpo, Po, Salween, Mekong, Yangtze, Yellow, Yalong, Dadu, and Min rivers in western China, relative to the epicenters of large earthquakes (M>4.9), and to zones of high to very high, moderate, and low seismic hazard. The locations of these major dams are based on the “ziyuan_b” map published by HydroChina and reproduced in Figure 2.7 There are more detailed maps on other websites which show additional dams,8 but these maps do not provide a reference grid or scale for location of these dams, so only the 137 dams shown on the rivers of western China in the “ziyuan_b” map, on the rivers listed above, are included in 9 this analysis (see Table 1). 2 The earthquake epicenter locations for all earthquakes within the map area with magnitudes (M) greater than 4.9 (M>4.9) in Figure 1 were obtained from the US Geological Survey earthquake database.10 M>4.9 was selected as the minimum because earthquakes of magnitude 5.0 or greater have been known to cause damage to dams and to other 11 structures (see Table 6). The USGS global database for the years 1973-2011 was utilized in this analysis because, prior to 1973, the location and magnitude of earthquakes in this area were estimated. Furthermore, prior to 1973, the focal point depths of This proposed earthquakes were unknown and impossible to estimate, therefore eliminating the usefulness of pre-1973 data in study must also assessing the risk for reservoir-induced seismicity caused be disclosed to by dams built in this area. The seismic hazard zones China’s citizens, depicted in Figure 1 are adapted from the Seismic Hazard press, power Map published in 1999 by the Global Seismic Hazard 12 companies, Assessment Program of the United Nations. In this financial extraordinary exercise, 500 scientists mapped the magnitude of horizontal shaking that can be expected in a institutions, and given place during a given time span for the entire world.13 law-makers to The base map showing major rivers and China’s boundary ensure an was obtained from Earth Science Resources Incorporated informed public (ESRI). debate. A database of cities and towns was constructed using coordinates obtained from Google Earth. The maps and statistical summaries were prepared using ESRI’s ArcGIS 10.0 software. The current status of dams on each river (Table 5) is based on an unpublished database of China’s dams by International Rivers and confirmed (to the extent possible) by close examination of the most recent satellite images by Google Earth. Analysis Once the dam, earthquake, and city/town databases were converted to map layers, these layers and the seismic hazard zone map were added to the base map. Table 1 summarizes data for the dams on each river as found in the ziyuan_b map. Table 2 summarizes data for the magnitude of earthquake epicenters and their focal point depth. Table 3 summarizes the percent of dams within each seismic hazard zone for each river, and Table 4 summarizes the 3 percent of total megawatt capacity within each seismic hazard zone for each river. While the risk analysis in this study is based on the ziyuan_b map of 137 dams either built, under construction, or planned for each of these rivers, in all likelihood, this database is incomplete and underestimates the number of dams on these rivers. Moreover, the status of the 137 dams has changed since 2004 (when the ziyuan_b map is believed to have been finished): Table 5 lists 66 dams that have been built or are under construction for each river in this region as of 2011. These 66 dams represent 48 percent of the 137 dams shown on the ziyuan_b map which, in 2004, recorded only 12 percent of the dams as built or under construction. This rapid rate of dam construction … 98.6 percent of demonstrates that this study’s assessment of the risk from all of these dams, dam building in this region is likely to be an underestimate.