Earthq Sci (2019)32: 170–178 170 doi: 10.29382/eqs-2019-0170-07

Parameters of the AD 849 earthquake east of Baotou City in Inner Mongolia and the adjustion of the potential seismic sources zone spatial distribution functions*

Ji Wang1,* Zhanwu Gao1 Wei Xu1 Zhaode Yuan2 Zhicheng Liu1 Xiaoliang Zhang1

1 China Earthquake Disaster Prevention Center, Beijing 100029, China 2 Institute of Geology, China Earthquake Administration, Beijing 100029, China

Abstract According to volume 18 (Xuanzong Ji records the following: “Xinsi Age in October of the third Tang) of the historical book entitled the Old Book of Tang, the year of Dazhong Emporer in Tang Dynasty (October 20, Hetao area of Inner Mongolia experienced a large earthquake AD 849), the Jingshi (Xi'an City) felt earthquake shock in AD 849. However, previous work on that earthquake contains many discrepancies regarding its epicenter location, and Hexi, Tiande, Ling, Xia felt especially serious. magnitude, deaths, and intensity. While exploring active Thousands of people were killed”. This indicates the faults in Baotou City, the present authors mapped the Daqing historical occurrence of a great earthquake in the north of Mountain piedmont fault geologically. Based on previous China, but the scant historical records and the nearly 1200 work, several seismic deformation traces of more than 1000 years that have elapsed since the earthquake mean that years ago were found, and dating tests were conducted. The little trace of it remains. Nie and Li (1991), and Nie et al. research showed the Daqing Mountain piedmont fault zone to (1996, 2008, 2010) studied the AD 849 earthquake in be the seismogenic structure of the AD 849 earthquake. The length of earthquake surface rupture zone was around 80 km, detail and suggested the Daqing Mountain piedmont fault and the macro epicenter was located in the active fault. The as the causative fault. His work showed that the earthquake deformation center was located at 40.6°N, 110.2°E. By fault starts at Haolaigou in the west and extends eastward collecting and analyzing more historical data about the AD intermittently to the Baiyunchahan area of the Tumed Left 849 earthquake, reinterpreting some existing historical data, Banner. The length of the surface rupture zone is about and re-examining the contradictory numbers of deaths in the 100 km. The accumulated vertical displacement measured historical data, the present analysis concludes that around 10,000 people were dead. It is suggested that this earthquake by Nie et al. (2010) was more than 2.3 m, from which he had a magnitude of 7½. According to the revised seismic judged that the epicenter intensity could have been as high parameters and the paleoearthquake recurrence period of the as intensity of Ⅹ degree. Daqing Mountain piedmont fault, the boundary of some However, Nie et al. (2010) estimated the death toll potential seismic sources zone in the Baotou area are adjusted being only in the dozens, which seems somewhat and the recurrence period of M8 and M7.5 are re-calculated. inconsistent with the scale of economic and population damage caused by a major earthquake at that time. In the Keywords: earthquake; rupture traces; parameters; AD 849; present study, data about this earthquake were collected Daqing Mountain; piedmont fault systematically and then sorted and examined. Here in, we discuss the epicenter location, the seismogenic structure and isoseisms, the number of death toll, and the magnitude 1 Introduction of the earthquake. Having revised the seismic parameters, we adjust the boundary and parameters of some seismic potential sources zone in the Baotou area. Volume 18 (Xuanzong Ji) of the Old Book of Tang

* Received 22 May 2019; accepted in revised form 6 January 2020; 2 Epicenter of AD 849 Baotou east published 29 May 2020. earthquake * Corresponding author. e-mail: [email protected] © The Seismological Society of China and Institute of Geophysics, China Earthquake Administration 2019 To determine the epicenter of the AD 849 east Baotou

Earthq Sci (2019)32: 170–178 171 earthquake, we begin by establishing the present locations located on the East Bank of the Yellow River in the of some of the places named in historical books. Speci- northwest of Wuzhong City, Ningxia Hui Autonomous fically, Jingshi or Shangdu refers to the capital City of the Region (Lu et al., 1993). Tang Dynasty, which is now Xi’an City in Shaanxi Prov- Yanzhou City is located in Dingbian County in ince. Meanwhile, Zhenwu and Tiande were important mili- Shaanxi Province. tary organizations on the northern frontier of the middle to Xiazhou is now Baichengzi Village of Hongdunjie late Tang Dynasty (AD 755–907) and were also known as Town in Jingbian County in Shaanxi Province. the Zhenwu Army and Tiande Army, respectively. Yunjia Town, namely, Yunjiaguan pass, this showed The Zhenwu Army, established in the second year of that Yunjiaguan pass belonged to Jinhe County. It should the Jinglong Age of the Tang Dynasty (AD 708), located be in the area of Helinger County of Inner Mongolia in Tuchengzi township, Helinger county, Inner Mongolia, (Table 1). according to the Eighteenth Geographical records of the In summary, the locations of heavy death toll due to Old Book of Tang (Liu, 1975 a, b). the earthquake were all in and around the Hetao Basin. Tiande Army, belonging to Guan-nei Dao, Tang Considering the seismic geological conditions of the Hetao Dynasty, was stationed on the south bank of Wuliangsu Basin and its surrounding areas, we conclude that the Sea, the Urad Front Banner, Inner Mongolia. earthquake almost certainly occurred in the Hetao Basin, a Lingwu, namely, Lingzhou City of Tang Dynasty was conclusion that is supported by previous research (Nie and

Table 1 Ancient places name and its modern location and destruetion associated with AD 849 earthquake

No. Ancient place name Modern location Destruction Intensity

1 East Shouxiang City Old Town of Tuoketuo County, Thousands of soldiers X Inner Mongolia were dead

2 Chanyu Grand Frontier Command Tuchengzi Township, Helinger County, (location of Zhenwu Army) Inner Mongolia

3 Shengzhou City South bank of Yellow River in Zhungeer Banner, Inner Mongolia Army towns and farm 4 Mid Shouxiang City North bank of Yellow River in south of Baotou City, houses destroyed ≥VIII Inner Mongolia

5 Tiande Army South coast of Wuliangsu Sea in Wulat Qian Banner, Inner Mongolia

6 Yunjia Town Helinger County, Inner Mongolia Two captains and tens soldiers were killed

7 West Shouxiang City Wulat Qian Banner of Inner Mongolia Earthquake had VII sound, farm houses 8 Linzhou Shenmu County, Shaanxi Province destroyed 9 Ma Yi Shuozhou City, Shanxi Province

10 Lingzhou East bank of Yellow River in northwest of Wuzhong Earthquake was strong VI City, Ningxia Hui Autonomous Region and may have caused some damages 11 Xiazhou Baichengzi Village, Hongdunjie Town, Jingbian County, Shaanxi Province

12 Yanzhou Dingbian County, Shaanxi Province

13 Jingshi Xi′an City, Shaanxi Province Felt a little shock

14 Tongzhou Dali County, Shaanxi Province Felt a little shock

15 Yulin Yulin City, Shaanxi Province Felt a little shock

16 Huaiyuan Hengshan County, Shaanxi Province Felt a little shock

17 Xining Xining City, Qinghai Province Felt a little shock

18 Zhili Hebei Province Felt a little shock

19 Shanxi Shanxi Province Felt a little shock

172 Earthq Sci (2019)32: 170–178

Li, 1988, 1991; Nie et al., 1996, 2008, 2010). platform has a 14C age of 2507±122 a, and the vertical displacement of the fault is 0.85 m (Nie et al., 2010). 3 Fracture range and location of 4) North of the expressway bridge of Yongfu Village, a epicenter region Holocene alluvial fan (with a 14C age of 4610±90 a at the top) is arched and deformed, and a group of more than 10 faults with different scales has developed (Nie et al., Next, we discuss the seismogenic structure and more- 2010). accurate epicenter location of this earthquake based on the 5) On the front of the Hazigai diluvial fan in Goumen results of recent seismogeological studies. Nie et al. (1996) Town of Tumed Right Banner, the fault dislocation strata uncovered 6 ancient earthquake events since the Holocene have a 14C age of 2310±100 a (Jiang et al., 2001). by digging a trench in an aluminum plant. In the middle 6) In the Shangdalai trench in the Tumed Left Banner, and western segments of the fault, traces of seismic the fault dislocation was around 1 m from the surface. The deformation about 1000 years ago have been found in layer contains Han Dynasty pottery tablets, and its 14C age many places. The main relics are as follows. is 2115±105 a (Wu et al., 1995). 1) A fault scarp of 2.6–2.7 m in height is developed in 7) At the front of the Baiyunchahan estuary alluvial fan the rear edge of the level-I platform in the west of Xuehai in Qianzhan Village of Tumed Left Banner, the age of 14C Gully, whose strike approaches nearly E-W and extends to fault dislocation was 1160±100 a (Jiang et al., 2001). 500 m. The latest activity of faults controlling steep ridges The aforementioned seismic deformation traces along 14 disrupted the grayish-brown sandy soil layer with a C the Daqing Mountain piedmont fault are distributed age of 1640±112 a, with a fault displacement of 1.2 m (Nie between the Donghe District of Baotou City and the et al., 2010). Tumed Left Banner of Hohhot City, with a length of 2) In the north trench trough of the Baotou Aluminum around 80 km from east to west and concentrated in the Plant (Nie et al., 1996), the latest fault activity is a stratum area from the Baotou Aluminum Plant to Yongfu Village. with a staggered moluminescence age of 1280±70 years Therefore, we consider these to be traces of the AD 849 ago. earthquake and that the Daqing Mountain piedmont fault is 3) There are two distinct preserved seismic scarps on the seismogenic fault of the AD 849 earthquake, whose the level-I platform (newest terrace) of Ashangoumen epicenter was located in the area from the Baotou Village, extending in the ENE-EW directions, with a Aluminum Plant to Yongfu Village. We suggest that the visible length of over 500 m and heights of 0.28 m and epicenter should be revised to 40.6°N, 110.2°E, which is 0.42 m, respectively. The distance between them is around consistent with the above description (Figure 1). Nie et al. 30 m. A trench was excavated across the front of a steep (2010) gave the geographic coordinates as 40.4°N, ridge, and it could be seen that the steep ridge is controlled 110.2°E, but that location is around 20 km far from place by a south-dipping normal fault dipping southward. The of the Daqing Mountain piedmont fault and is inconsistent gray-black paleosoil layer on the top of the staggered with the reference geographical names mentioned above

109°E 110° 111° 112°

West Shouxiang

Inner Mongolia Autonomous Region

M71/ -2 849-10-20 41°N

Hohhot Tiande Army Baolvtanca Xuehaigou Hazigai Shangdalai Urat Front Ashangou Baotou Yongfu Ⅷ Yellow River Yunjia Army Mid Shouxiang Zhenwu Army Togtoh Helingeer Ⅵ—Ⅶ

0 25 50 km Shengzhou 40° Now place name Old place names Fault profile points Seismic rupture zone Figure 1 Distribution map of meizoseismal areas

Earthq Sci (2019)32: 170–178 173

(Baotou Aluminum Plant to the Yongfu Village area). The New Book of Tang (Ouyang, 1975a) records the Damaging range: Baotou to Yanzhou (Dingbian), following: “The earthquake shocks were felt in Shangdu. Xiazhou (Jingbian), Lingzhou (Wuzhong), had an average In Zhenwu, Hexi, Tiande, Lingwu, Yanxia and other city radius of around 400 km. Xining City was the farthest the earthquake damaged houses, killed dozens of people.” place in which the earthquake was felt shock, with a radius The earthquake impact range recorded in the New Book of of around 830 km (Figure 2). Tang (Ouyang, 1975b) is basically the same as that in the Old Book of Tang, but the death toll is quite different. The 4 Analysis of death toll in AD 849 Old Book of Tang was published in the second year of the Kaiyun Age of the HouJin Dynasty (AD 945) and edited earthquake on the basis of the past national history (Chen, 2006, Yan et al., 1992). Soon after the Tang Dynasty, the sources of The earthquake shock was felt in Xi′an, the capital of information were abundant and detail. The New Book of Tang Dynasty, with no obvious damage. The damage Tang (Ouyang, 1975c) was completed in the fifth year of occurred mainly in Hexi, Tiande, Lingzhou, and Xiazhou, the Jiayou Age of Emperor Renzong in the Song Dynasty where thousands of soldiers were crushed to death. (AD 1060), more than 100 years after the Old Book of However, the historical data do not include the number of Tang. Therefore, the death toll recorded in the New Book inhabitants who were killed; if that number was included, of Tang may be incorrect. Moreover, an earthquake with then the death toll could be several times greater. such a large impact would have been one with a large

105°E 110°

Yunjia West Shouxiang Ashangou Yongfu Baolvtancan Shangdalai Hazigai Hohhot Xuehaigou Baotou Ⅷ Zhenwu Arm Togtoh Mid Shouxi East Shouxiang Shengzhou 40°N

Ⅵ -Ⅶ Zhungeer Qi Mayi

Shuozhou

LinzhouYellow Yinchuan Ⅴ -Ⅵ Yulin Lingzhou Hengshan Wuwei River Wuzhong Yanzhou Xiazhou Taiyuan

Ⅳ Xining

Yellow

River Lanzhou

35° Tongzhou

Dali 0 50 100 km Xi'an

Current place names Old place names Fault profile points Seismic rupture zone Figure 2 Intensity of AD 849 Baotou east earthquake

174 Earthq Sci (2019)32: 170–178 magnitude and that could not have killed only dozens of policy of Mang Wang when he was in power, the Huns people. Moreover, “ten” may have been a miswriting of invaded continuously southward, forcing the residents of “thousand”. “Ten” and “thousand” are closer in Chinese Jiuyuan City to flee southward, and the city went into writing. The writing of the Chinese characters “Ten” and decline. Because of the decline of the Han Dynasty, by the “Thousand” has not been changed. end of the Eastern-Han Dynasty, the northern nomadic Regarding the earthquake, the Institutional History of people were strong. Facing constant attacks from those the Tang Dynasty records the following in particular: nomadic people, the residents of Jiuyuan City abandoned it “(The earthquake) Crushing military bases and houses, the and moved southward. captain of Yunjia Town and the captain of soldiers and Up to AD 856, this shows that the early Tang Dynasty horses from Hubei Province for prevention of robbery in ruled the Hetao area effectively. In the mid-Tang Dynasty, autumn and tens soldiers were killed.” Dozens of people the Tiande Army and Zhenwu Army were added to defend died in Yunjia Town, so the number of people killed in this the area, and Mid Shouxiang City was built on the original earthquake was not as little as the dozens recorded in the site of Jiuyuan City, becoming a transportation hub and New Book of Tang. We reason thousands of soldiers as important military town connecting east, west, north, and having been killed, which is closer to the truth than tens of south. This shows that the Hetao area was relatively people. How many troops were stationed in the Hetao area prosperous and economically developed at that time, and at that time? If thousands of soldiers died, what was the there would have been tens of thousands of people living death rate of the entire soldier? there. Therefore, on the basis of a death toll of 10%, we Shuofang warlord had 7,000 soldiers and 1,700 horses. estimate that at least several thousand common people Zhenwu Army had 9,000 soldiers and 1,600 horses. The would have died. Tiande Army had more than 10,000 soldiers. The Anbei Analyzing the above historical records confirms that a Protectorate had 6,000 soldiers and 2,000 horses. In large earthquake occurred in northern China in AD 849. summary, the total troops of the Hetao area was around The earthquake killed thousands of soldiers in the Tiande 32,000 soldiers, with around 5,300 horses. If thousands of Army and Zhenwu Army stationed in the Hetao Basin and people died, the death rate corresponds to around one tenth thousands of inhibitants. Overall, the earthquake may have of the troops. killed nearly ten thousands people. At that time, in addition to the troops stationed in Hetao, were there also inhabitants living there? The history 5 Magnitude of AD 849 earthquake of Hetao shows that during the Warring States Period, Zhao State troops swept across northern Shaanxi and East of Baotou southern Inner Mongolia and drove the Huns to the north of Ura Mountain. They established Yunzhong County of Previous views differ regarding the magnitude of this today’s Inner Mongolia, and built the Great Wall along earthquake. Based on the epicenter intensity, the length of Ura Mountain, which was a section of the famous Great the surface rupture zone, the range of damage, and the Wall of Zhao. That is to say, a large city was built in the range of feeling shock, Sun (1985), Wu (1989), Huang southern part of Hadmengou Pass, namely Jiuyuan City, in (1989), Department of Earthquake Disaster Prevention, which many troops were stationed. This made it a military China Seismological Bureau (1995), and Nie et al. (2010) town in the northwest of Zhao State, effectively gave earthquake magnitudes in the range of 7.3–8.2. guaranteeing the safety of the northern part of Yunzhong Clearly, the magnitude of the AD 849 earthquake has Prefecture. The Qin Dynasty established Jiuyuan Prefecture, been recognized differently. From areas in which the one of 36 Prefectures (Sima, 2005). earthquake intensity could be determined, a series of In 127 BC, Jiuyuan Prefecture was renamed Wuyuan empirical relations has been established using the Prefecture, which had 16 counties under its jurisdiction. statistical analysis of magnitude. These empirical relations The immigration of inland immigrants, the development of can then be used to calculate the magnitude where the agriculture, and the use of advanced production methods earthquake intensity cannot be determined. However, if the meant that this area became highly developed. Wuyuan earthquake fault has been investigated fully, the magnitude Prefecture became an important agricultural reclamation can also be obtained by using the established statistical area in the Han Dynasty, and Jiuyuan City also developed empirical relationship based on the dislocation and length accordingly. By the end of the Western-Han Dynasty, of fault surface rupture zone. Deng et al. (1993) studied because of the rise of the Huns and the decline of the earthquake faults in China and noted that only earthquakes Western-Han Dynasty, as well as the incorrect foreign with M ≥ 7 can have earthquake fractures. Therefore, the

Earthq Sci (2019)32: 170–178 175 magnitude of the earthquake in AD 849 was undoubtedly Much work has been done on the relationship between greater than M7. Based on the characteristics of the magnitude and type, length of fracture, and displacement, earthquake intensity and surface rupture zone, we and various empirical relationships have been established, determine the magnitude of the AD 849 earthquake east of including that by Deng et al. (1993). The empirical Baotou as follows. relationship is M=7.20+0.31log(L) + 0.57log(D), which 1) Determine the magnitude according to the seismic gives M=8.0 with L = 80 km and D = 2.3 m. Based on that intensity. result, we determined the magnitude of the AD 849 a) Calculate the magnitude (M) according to the earthquake east of Baotou finally as 7.62±0.5. From the magnitude rule of historical earthquakes in China, we epicenter intensity (I0); suggests that the magnitude of this earthquake is 7½±0.5. M = 0.67I0 + 0.66, M = 7.36 (Liu, 1989) M = 0.61I0 + 1.42, M = 7.52 (Wu, 1989) M = 0.58I0 + 1.5, M = 7.3 [(Institute of Geophysics, 6 Potential seismic sources zone border China Seismological Bureau and Institute of Chinese and parameters adjustment in Baotou Historical Geography, Fudan University, 1990)] Area and its significance b) Calculate the magnitude (M) according to the epicentral distance (R) of areas of different intensity. The neotectonic movement in the Baotou area was M = 5.02 + 1.21log(R), R = 140, M = 7.62 characterized mainly by the strong subsidence of the Hetao M = 1.38 +2.32log(RV), R = 450, M = 7.53 fault basin and the uplift of the surrounding blocks. It can M = 0.25 + 2.54log(R), R = 830, M = 7.66( Liu, 1989) be divided into three neotectonic units, namely the M = 1.93+2.06log(R), RV = 450, M = 7.39 (Wu, 1989) Yinshan Mountain uplift, the Hetao basin, and the Ordos c) Calculate the magnitude (M) according to range of uplift (Figure 3). the feeling shock (D) The Yinshan Mountain uplift area is in the north of the log(D) = 0.22M+1.11, D = 830, M = 8.22 region, which comprises a series of near-EW mountains, 7.5 < M < 8 (Institute of Geophysics, China Seismo- including Serteng Mountain, Wula Mountain, and Daqing logical Bureau and Institute of Chinese Historical Mountain. Controlled by the active faults in front of it, Geography, Fudan University, 1990) Yinshan Mountain has been uplifted to form a tilted fault- 2) We determined the magnitude according to the sur- block mountain with south-north tilts. Since the Cenozoic, face rupture zone. For that relationship, the type of rupture the piedmont Hetao Basin has been subsiding continuously zone of the earthquake has been discussed previously. and forming the broad Hetao Plain, and the geomorphic

109°E 110° 111° 112° 42°N

Yinshan Uplift

2300

F3 41° Hetao Basin Yinshan Uplift Baotou Hohhot F2 F1 Hetao Basin Elevation (m)

40° Ordos Block 800 Dongsheng

Surface fault Buried fault

0 50 100 km

Figure 3 Regional geological structure in Baotou. F1: Daqing Mountain piedmont fault; F2: Wula Mountain piedmont fault; F3: Serteng Mountain piedmont fault

176 Earthq Sci (2019)32: 170–178 boundary between the mountain and the plain is obvious. Banner M8, and Baotou M7.5) two along the Wula Hetao Basin is a compound basin that can be divided Mountain piedmont fault (namely Baotou M7 and Urad into three depressions in the left and right steps. These Front Banner M7), and three along the Serteng Mountain three depressions are controlled by the piedmont fault piedmont fault (namely Hassatu M7, Dashetai M7, and zones of ① Lang Mountain and Serteng Mountain, ② Wujia River M7.5). The maximum probable earthquakes Wula Mountain, and ③ Daqing Mountain and are of the seismic potential sources zone in the other areas are basically dustpan-like fault depressions that are deep in the M6.0 or M6.5. north and shallow in the south. The Hetao fault depression We used the above research results to adjust the zone is an active seismic zone with large magnitude and boundary between the potential seismic sources zone of high frequency. the Tumed Right Banner and Baotou City (Figure 4). The The Ordos uplift is a relatively complete uplift area potential seismic source zone of the Tumed Right Banner with weak internal deformation. The block is surrounded expanded to the west, including the epicenter of the AD by faults and fault basins. As a stable area, the Ordos block 849 earthquake. has been in a state of uplift since the neotectonic period. Based on Holocene paleoearthquake events in Daqing There has been no active structure or strong earthquake in Mountain (Gao et al, 2014), there may have been three the uplift area. It is a continental block with strong paleoearthquakes in the Baotou section since the integrity and no structural activity differentiation. Holocene, with age values of 7.6 Ka BP, 5.5 Ka BP, and We identified four potential seismic sources zone 1.2 Ka BP from old to new. The spatial distribution along the Daqing Mountain piedmont fault (namely functions of the potential seismic sources zone of the Hohhot M7, Tumed Left Banner M7.5, Tumed Right Tumed Right Banner were increased accordingly, as given

108°E 109° 110° 111° 112° 42°N

Ulat Central Banner

4（7.5）

Wuyuan Guyang 9(6.5) 41° 5（7） 8（7） 6（7） 1 10(6.5) 7 /2(849.10.20) Hohhot City * Ulat Front Flag Banner Tummett Left Banner 1（8） 12(6) 7(7) Baotou 3（7.5） Tummett Right Banner 11(6.5) Togtoh 13(6) （ ） 2 7.5 Dalate banner 14(6) Helinger County

40°

Qingshuihe Number 1(8.0) Dongsheng (maxi magnitude) Q4 fracture Zhungeer Banner

Q3 fracture

Potential source Pianguan 0 25 50 km

Figure 4 Distribution map of potential source areas in Baotou Area

Earthq Sci (2019)32: 170–178 177 in Table 2. It can seen that the recurrence period of the thquakes by 2100 a but became 1500 a after this original M8 earthquake before adjustment was 2450 a, adjustment. The recurrence period of the original M7.5 which exceeded the shortest recurrence period of paleoear- earthquake was adjusted from 1070 a to 830 a.

Table 2 Annual incidence rate and spatial distribution function adjustment.

M7.0–7.4 M ≥ 7.5

Spatial Spatial Seismic belt/Potential source Annual Recurrence Annual Recurrence distribution distribution incidence rate cycle (year) incidence rate cycle function function

Yinchuan-Hetao seismic belt 1 0.00891 112 - 0.00316 316

Tumed Right Banner Before adjustment 0.10489 0.0009346 1070 0.1286 0.0004065 2450

After adjustment 0.1349 0.001202 830 0.2086 0.000659 1500

Baotou 0.1714 0.00160 630 -

7 Conclusions References

Chen Y (2 006) Old Book of Tang and New Book of Tang. Teaching 1) The range of continuous distribution of seismic Problems of History 28(4): 63–65 (in Chinese) surface rupture traces is about 80 km. It is the same as the Deng QD, Yu GH and Ye WH (1 993) Study on the relationship length of seismic surface rupture zone in the Daqing between surface rupture parameters and magnitude of Mountain piedmont fault zone. These identified Daqing earthquakes by active faults study. Beijing, Seismological Press, Mountain piedmont fault is the seismogenic structure of pp 247–264. the AD 849 earthquake. Gao ZW, Xu W, Yuan ZD, Liu ZC and Wang J (2 014) Subtopic 2) According to the research and historical data of the Report of Baotou Active Fault Detection and Seismic Risk Daqing Mountain piedmont fault zone, the epicenter of the Assessment Project: Research on Active Fault Paleoseismic AD 849 earthquake was in the area from the Baotou Trench. China Earthquake Disaster Prevention Center, Beijing, pp1–39 Aluminum Plant to Yongfu Village, with geographic Department of Earthquake Disaster Prevention, China Seismological coordinates of 40.6°N, 110.2°E and a magnitude of 7½. Bureau (1 995). Catalogue of Strong Earthquakes in Chinese The suggestion is that this earthquake be named the AD History (23rd Century BC–AD 1 911). Beijing, Seismological 849 earthquake East of Baotou 7½ magnitude in Inner Press, pp16–17

Mongolia. Huang SM (1 989) Discussion on the magnitude balance of large 3) According to historical data, the AD 849 earthquake earthquakes with M8 in China. Collection of Chinese Historical East of Baotou damaged the houses of the military towns, Earthquake Studies. Beijing, Seismological Press, pp131–133 killed nearly 10,000 people, with an epicenter intensity of Institute of Geophysics, China Seismological Bureau and Institute of X degree. Chinese Historical Geography, Fudan University (1 990) 4) Using the place of epicenter of the AD 849 Historical Seismological Atlas of China (Ancient to Yuan earthquake, the boundary of the Tumed Right Banner Dynasty). Beijing, China Map Publishing House, p98 potential source zone was adjusted. Because the magnitude Jiang WL, Xiao ZM, Wang HZ and Gong FH (2 001) Segmentation characteristics of seismic rupture in Daqing mountain Piedmont of AD 849 earthquake was increased from M7 to M7½, active fault zone. Inner Mongolia Seismology 23(1): 24–34 the recurrence period was decreased. Recurrence period Lu RY, Wu ZL and Xuzhuang (1 993) Textual Research on History of M8 were adjusted to 1500 a and M7.5 was adjusted and Geography of Ningxia. Yinchuan, People's Publishing House to 830 a. Liu H (1 975a) The Old Book of Tang (Volume 18) Bibliography 18: Xuanzong Ji. Zhonghua Bookstore, Beijing p625 Acknowledgments Liu H (1 975b) Old Book of Tang (Volume 37): Zhi 17: Wuxing Zhi. Zhonghua Bookstore, Beijing

Liu CS (1 989) Revision opinions on some historical seismic This work was supported by a subproject of the parameters. Collection of Chinese Historical Seismic Research 1. strategic leading science and technology project (A) of the Beijing, Seismological Press, pp62–67

Chinese Academy of Sciences (No.XDA20070302)”and Nie ZS and Li K (1 988) Discovery of the Salawusu Formation in the we thank the reviewers and editors for their suggestions Baotou area of Inner Mongolia and its significance. Sci Bull and opinions. 33(21): 1 645–1 649

178 Earthq Sci (2019)32: 170–178

Nie ZS and Li K (1 991) Discussion on the great earthquake in Hetao Xuanzong Ji. Beijing, Zhonghua Bookstore

Area, Inner Mongolia, AD 849. In: Guo ZJ ed. Collection of Ouyang X and Song Q (1 975c) New Book of Tang (IV), Vol. 37, Zhi Historical Earthquakes in China 2. Beijing, Seismological Press, 27 Geographical Records. Zhonghua Bookstore, Beijing

pp125–127 (in Chinese) Sun JL (1 985) The risk of strong earthquake in the northern margin Nie ZS, Jiang WL and Wu WM (1 996) Study on Holocene of Ordos block. Journal of Northwest Seismology 7(s1) : 13–23 Paleoearthquakes in the Western Section of Daqing mountain Sima G (2 005) General knowledge of Zizhi Volume 7. Beijing， Piedmont Fault Zone, Inner Mongolia. In: Institute of Geology, Zhonghua Bookstore China Earthquake Administration: Theory and Application of Wu HY (1 989) Estimation of magnitude of historical earthquakes. Active Fault Research,. Beijing: Seismological Press pp In: Min ZQ and Guo ZJ eds. Collection of Chinese Historical 125–135. Earthquakes Research. Beijing, Seismological Press, pp62–67 Nie ZS, Li H and Ma BQ (2 008) Late Pleistocene fossil fauna. Wu WM, Li K, Ma BQ, Yang F and Guo WS (1 995) Holocene Quaternary Study 28(1): 14–25 paleoseismological study of large combined troughs in Daqing Nie ZS, Wu WM and Ma BQ (2 010) Surface fracture zone and seismic parameters of AD 849 Baotou East Earthquake, Inner mountain piedmont fault zone. In: Institute of Geology, National Mongolia. J Seismol 32(1): 94–107 Seismological Bureau ed. Theory and Application of Active

Ouyang X and Song Q (1 975a) New Book of Tang (Volume 35): Fault Research. Seismological Press, Beijing,

Wuxing Zhi. Beijing, Zhonghua Bookstore Yan ZJ (1 992) Demonstration of the historical sources of Old Books

Ouyang Xiu and Song Qi (1 975b). New Book of Tang Volume 8, of Tang. Journal of Liaoning University 34(6): 8–11