Vol.2, No.3, 160-174 (2010) Natural Science
http://dx.doi.org/10.4236/ns.2010.23026
Surface rupture and hazard characteristics of the
Wenchuan Ms 8.0 earthquake, Sichuan, China﹡
Rong-Jun Zhou1, Yong Li2, Liang Yan2, Jian-Cheng Lei1, Yi Zhang2, Yu-Lin He1,
Long-Shen Chen3, Xiao-Gang Li1, Shi-Yuan Wang1, You-Qing Ye1, Yu-Fa Liu1,
Chuan-Chuan Kang 1, Tian-Yong Ge 1, Qiang He1, Wei Huang1
1Institute of Engineering Seismology of Earthquake Administration of Sichuan Province, Chengdu, China
2State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, China;
3The University of Hong Kong, Department of Geology, Hong Kong, China
Received 23 December 2009; revised 14 January 2010; accepted 25 January 2010.
ABSTRACT
Longmen Shan is located the special joint be-
tween Tibetan Plateau inland in the west and
Yangtze craton in the east. Consisting of a se-
ries of parallel imbricated thrust, it develops,
from the west to the east, the Maoxian-
Wenchuan, Beichuan-Yingxiu and Pengxian-
Guanxian faults. The Wenchuan earthquake is a
thrust with strike-slip type, and thre surface
ruptures are located on the Beichuan-Yingxiu
fault zone and Pengxian-Guanxian fault zone.
The surface rupture on the Beichuan-Yingxiu
fault shows the thrust and dextral slip charac-
teristic. The maximum vertical displacement of
the surface rupture is about 10.3 m and the maxi-
mum right-lateral displacement is about 5.85m.
Though the vertical displacements and the hori-
zontal displacements in the different segments
have certain differences, as a whole, the ratio of
the vertical displacement and the horizontal dis-
placement is close to 1:1. The surface rupture on
the Pengxian-Guanxian fault shows thrust and
dextral characteristic. The rates of vertical dis-
placements and the horizontal displacements
ones on the most other segments are between
1:3 and 1:2. So the Beichuan- Yingxiu fault is a
dextral-slip and thrust fault and the average ver-
tical displacement is equal to the average hori-
zontal displacement, while the Pengxian- Guan
xian fault is thrust fault with a little dextral-slip
component. The total intensity area above Ⅵ de-
gree of the Wenchuan earthquake is about 333000
km2. The high earthquake intensity line stretches
to N40-50°E along Longmen Shan tectonic belt.
The rate of the long axis and the minor is betw-
een 8:1 and 10:1. Three Ⅺ intensity regions are
isolated in distribution. It presents a multipoint
instantaneous characteristic of the rupture.
Keywords: Wenchuan earthquake; Longmen Shan;
Surface rupture; Hazard; Sichuan; China
1. INTRODUCTION
According to the record of China earthquake networks,
on 12th May, 2008, a huge earthquake Ms8.0 struck
Yingxiu town in Wenchuan county, Sichuan province
(31°00′N, 103°24′E). The earthquake took place at
14:28:04(Beijing time) and the depth of its hypocenter is
about 14 kilometers. This earthquake with high magni-
tude and shallow hypocenter made an astonished attack
on Longmen Shan area, which is located in the west of
Sichuan basin, resulting in tremendous casualties and
property losses. The earthquake occurred on Longmen
Shan tectonic belt at the eastern margin of the Tibet Pla-
teau. Since the late Cenozoic, the thrust-dextral move-
ment of Longmen Shan tectonic belt led to Longmen
Shan Mt.’s fast uplifting in opposition to Sichuan basin.
Within the range of 50 kilometers along Longmen Shan
tectonic belt, topographical fall exceeds 5 kilometers,
which produces mountains and canyons region [1-5].
The special terrain and geology condition increased the
damage of this earthquake.
As soon as the earthquake occurred, the writer went to
Earthquake-stricken area to carry out an on-the-spot in-
vestigation for more than twenty days, accompanying
the earthquake emergency job team of China Earthquake
Administration. Some replenish investigations were car-
ried out later. Mountain fall, the earth splits, changes of
mountains and rivers caused by the earthquake made
Longmen Shan full of distress everywhere, which was
﹡This research was supported by China National Natural Science
Foundation grant 40841010, 40972083 and China National Science and
Technology supporting Plan Foundation grant 2006BAC13B02-07,
2006BAC13B01-604.

R. J. Zhou et al. / Natural Science 2 (2010) 160-174
161
elegant and pretty in the past. The enormous casualties
and property losses that the earthquake brought about are
furthermore grieved. Being greatly shocked and regretful,
we illuminate the first step survey results of surface rup-
ture and hazard characteristic of the earthquake and our
thoughts about it in this paper, providing a reference for
our fraternity. Especially, this paper was devoted to those
who had been died or disappeared in this destructive
earthquake.
2. THE SURFACE RUPTURE OF THE
WENCHUAN EARTHQUAKE
The Longmen Shan tectonic belt stretches through the
central of Sichuan province at N40-50°E orientation and
forms the boundary of the Songpan-Garzê orogenic belt
and the Yangtze Platform[1,6-8]. In late Triassic, the clo-
sure of Neo-Tethys Ocean resulted in the Longmen Shan
tectonic thrusting from northwest to southeast. It con-
trolled the formation and development of the Cenozonic
foreland basin in the southwest of the Sichuan basin.
There is a suit of mauve late Triassic - Cenozonic clastic
rock of river and lake facies. Since late Cenozonic, with
the closure of Neo-Tethys Ocean and fast-uplift of Qing-
hai-Tibet Plateau, neotectonic activities of Longmen Shan
tectonic belt have aroused many researchers’ interest.
Avouac and Tapponnier [9] believed that Longmen Shan
tectonic belt shortens sustainably at the NW-SE orienta-
tion, with a rate of 20mm/yr since late Cenozoic. But
through field works, Burchfiel [1] found that there was
lack of geological evidence for a large-scale shortening of
Longmen Shan tectonic belt and the west of Sichuan basin.
Data measured by the Global Positioning System(GPS)
cross Longmen Shan tectonic belt shows that the shorten-
ing rate of it is only 4.0 ± 2.0mm/yr, in opposition to that
of Sichuan basin [10]. However, England and Molnar [11]
pointed out that convergence between India plate and
Eurasia plate was reflected by a simple dextral-shear mo-
tion in the east margin of the Qinghai-Tibet Plateau. Fur-
thermore, Li Yong [3] believed that uplift of the Longmen
Shan was produced under the co-effect of the dextral mo-
tion and erode load-off of the Longmen Shan tectonic
belt.
The Longmen Shan tectonic belt is composed of
Maoxian-Wenchuan fault (the north-eastern segment is
called Pingwu-Qingchuan fault), Beichuan-Yingxiu fault
and Pengxian-Guanxian fault. There is a blind fault in the
front of the Longmen Shan Mountain (Figure 1). All of
these faults are late Pleistocence-Holocene active faults.
There are divergent opinions on the late Quaternary ac-
tivities of the Longmen Shan tectonic belt among differ-
ent scholars. Zhou [12] believe that the Longmen Shan
tectonic belt shows a thrust and dextral slip since late
Quaternary. The slip rate of single fault is about 1 mm/yr,
and the vertical component of displacement is equivalent
to the horizontal. However, Densmore [5] believe that the
average vertical slip rates of Beichuan-Yingxiu fault and
Pengxian-Guanxian fault are less than 1 mm/yr. The
horizontal slip rates of the faults are between 1mm/yr and
10mm/yr. And the faults show a dextral-slip characteristic.
The Wenchuan Ms8.0 earthquake, on 12th May, 2008,
produced coseismic displacements along Beichuan-
Yingxiu fault and Pengxian-Guanxian fault coinstanta-
neously. After the earthquake, a lot of geological experts
[13-23] carried out detailed investigations about the sur-
face rupture, caused by the Wenchuan earthquake, in the
Longmen Shan area. Therefore, it provides a good study
and a validated example for the late Quaternary activity
of the Longmen Shan tectonic belt.
2.1. The Surface Rupture on the
Beichuan-Yingxiu Fault
Beichuan-Yingxiu fault is also called Beichuan fault [5]
and is the major causative fault of the Wenchuan Ms8.0
earthquake on 12th May, 2008. The surface rupture on
this fault started near by Yingxiu town in Wenchuan
county and extended to the north-east. It is about 220
kilometers long, and crosses Hongkou town，Longmen
Shan town, Donglin temple, the north of Hongbai town,
Qingping town, Chaping town, Leigu town, Beichuan
town, Chenjiaba village, Fenghuang village of Guixi
town and Pingtong town, break down near Shikanzi vil-
lage in the east of Nanba town, Pingwu county.
1) The surface rupture of the Wenchuan Earthquake in
Yingxiu town
The epicenter of Wenchuan Ms8.0 earthquake is close
to Yingxiu town. The surface rupture of the earthquake
crosses the north of Yingxiu town in N60-70°E orienta-
tion. According to the different section features of the
surface ruptures, it can be inferred that inclination of the
fault is about 40-50°. In the north-west of Yingxiu town,
the vertical displacement of the national highway (G213)
is about 2 meters, and the dextral displacement is about
1.7 meters. A small waterfall was produced on a river
bed (Figure 2). Zhou [12] described that the vertical
displacement of Minjiang river’s terrace IV caused by
Beichuan-Yingxiu fault was about 40 meters. And the
bending fault produced a normal fault graben on the
hanging wall of the fault. This earthquake produced two
surface rupture zones on the fault scarp (close to its top)
with a horizontal distance of 6 meters. The vertical dis-
placement is about 0.75 meters and the horizontal dis-
placement is 1.1 meters at the low elevation place. At the
place with higher elevation, the vertical displacement
and the horizontal one are 2.4 meters, 1.9 meters, re-
spectively. And the total vertical displacement is 3.15
meters; the total horizontal displacement is 3.0 meters
(Figure 3). At the normal fault graben, it produced the
new normal fault scarp and tensile fractures. It is consis-
tent with the previous cognition. This phenomenon indi-
cates that the fault scarp on terrace IV is the accumula

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162
Figure 1. Distribution map for the surface rupture of the Wenchuan earthquake in Longmen Shan.
Figure 2. Sketch for the surface rupture of the Wenchuan earth-
quake in Yingxiu county.

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163
Figure 3. Fault scarp on the terrace IV of Minjiang river in the north of Yingxiu town. The photograph (a) was
shot on May, 2002. The photograph (b) was shot on July, 2008. The photograph c shows the vertical compo-
nent of the surface rupture. The photograph d shows the dextral horizontal displacement of the path.
Figure 4. The surface rupture of the Wenchuan earthquake in Hongkou region, Dujiangyan city. (a) the displacements
of the road at Shenxigou village; (b) the fault scarps at Bajiao temple.
tive displacement produced by several movement events
of the fault since late Quaternary and it has been under-
gone a-long-term denudated and back-off process.
2) The surface rupture of the Wenchuan Earthquake in
Hongkou town
The surface rupture extends at N50-60°E orientation
along the north-west bank of Baisha River near Hongkou
town in Dujiangyan city. It is about 16 kilometers long.
The maximum vertical displacement and the maximum
horizontal one are also about 5 meters. At Shenxigou
village, the surface rupture made a path displace with a
vertical component of 2.75 meters and a horizontal
component of 4.8 meters. Near Bajiaomiao paper mill
with a distance of 8 kilometers to the spot, the road, the
toft, tarrence I, the wash-land and the latter-day river bed
are all displaced 3.5 meters. The fault developed in the
Triassic coal stratum. There are two different phases
scarps on the fault plane, and the side angle of the hori-
zontal one is 43°. The scarp produced by this earthquake
is vertical approximately (Figure 4).
3) The surface rupture of the Wenchuan Earthquake in
Donglin temple.
Figure 5. Dislocation of road and split of pine tree in
Donglin temple, Longmen Shan town, Pengzhou county.

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At Donglin temple, 6 kilometers away to Longmen
Shan town at NE orientation(Baishui river), the surface
rupture zone extends at N45°E orientation, intersects with
a pathway with a small angle. The vertical displacement
of the pathway is 2.2 meters. A gully was displaced ver-
tically and produced drop water. There is a row of pine
trees along one side of the road. According to the local
residents’ description, the road and pine trees are straight
before the earthquake occurred. The road and pine trees
along the surface rupture zone produced right-lateral co-
seismic distortion. The horizontal displacement is 3.6 ±
1.0 m. The instantaneous offset of the fault resulted in the
pine trees inclined obviously, which are on the fault scarp.
One of the pine trees split and fell down because the ef-
fect of gravitation overlaid (Figure 5).
4) The surface rupture of the Wenchuan Earthquake in
Leigu town, Beichuan county
Near Leigu town of Beichuan county, the Beichuan-
Yingxiu fault divides into four branch faults arrange in
left-step en echelon. The result in the II proluvial fan and
streams vertical and dextral offset. The Gaitou hill in the
left-step area uplifted and Qianjiang river course was
changed [3,5,12]. The surface rupture of this earthquake
at Pingshang village in the north of Leigu town stretches
to N40°E, and made a list of gullies, pathways, proluvial
fan, road, water pipes, terrain I and river bed produce
vertical and right-lateral displacements (Figure 6). The
surface rupture shows that the north-west wall of the fault
uplifted and the south-east wall declined correspondingly.
Specially, Zhou [12] found a fault scarp with the height
of 22.5m and a gully with the right-lateral displacement
of 1.6 m before on the II level pluvial fan [12] (Figure 7).
At the same place, the surface rupture outcrops along the
preexisted fault scarp. The maximum vertical displace-
ment is 4.5 m. The displacements of gully and a pathway
are 1.6 m and the right-lateral dislocations of them are
1.43 m (Figure 8). At Zhaojiagou village with a distance
of 500 m to the spot, the vertical displacement of terrace I
is about 6.5m and the right-lateral one is 5.85m. But the
landslip maybe impacted on the precision of the dis-
placements measurement here.
The Liulin village in the west of Leigu town is near the
left-step area of the fault. There, the show of the surface
is more complicated. From north to south, the trend of the
surface rupture strikes from NE-trending to SN-trending
and NWW-trending (Figure 9).The NS-trending surface
rupture shows the vertical and left-lateral offset respec-
tively. The vertical displacement and the left-lateral off-
sets of a water slot are 1.9 m，1.3 m respectively. The
NWW-trending surface rupture shows the vertical and
right-lateral offset. The foundation of a house is cut off
by two cracks. The vertical displacements of two are
1.5 m，0.5 m respectively. And the right-lateral offsets of
them are 1.3, 0.3 m respectively (Figure 10).
5) The surface rupture of the Wenchuan Earthquake in
Figure 6. Distribution map for the surface ruptures of the
Wenchuan Earthquake in Pingshang village, Leigu town.
(a) the unworked airscape; (b) the worked airscape; the
black lines figure the distribution of the surface rupture,
the black-sawtooth lines shows the hanging wall of the
rupture; V: horizontal offset; H: vertical offset.
Maoba village, Beichuan county
Maoba village is about 300 m away to the northeast of
Beichuan county. The surface rupture of Beichuan-
Yingxiu fault is N40-50°E trending, and its vertical dis-
placements 4.7 m-10.3 m, which turns out to be a great
scarp with a characteristic of antithetic fault (Figure
11(a) ). The rupture incised the plat in the front of a
building with a vertical offset of 10.3 ± 0.2 m, and a hori-
zontal offset of 3.8 m (Figure 11(b)). About 200 m away
to the northeast of this point, the rupture cut a hummock.

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Figure 7. Displacements of the surface ruptures on the terrace
I and road in Pingshang village, Leigu town.
As effects of the right lateral component, there is a tri-
angular facet of fault in the edge of the hummock, and
the right-lateral offset of a field is 5.3 m (Figure 11(c)).
6) The surface rupture of the Wenchuan Earthquake in
Chenjiaba village
Chenjiaba village is about 15 kilometers away to the
northeast of Beichuan county. Here, the surface rupture
is about 200m long. The other segments of the surface
rupture are covered by landslides. The rupture is N35°E
trending and incised the river bed, floodplain, terrace I
and the pathway. The vertical displacements of them are
2.0 m, 1.7 m respectively. The right-lateral offset of them
are 1.6 m, 1.35 m respectively (Figure 12(a)).
7) The surface rupture of the Wenchuan Earthquake in
Fenghuang village, Guixi town
Fenghuang village is about 2 kilometers away to the
northwest of Guixi town. The vertical displacement of a
Figure 8. Displacements of the surface ruptures on the terrace II and gully in Pingshang village, Leigu town. (a) The photograph
was shot on April, 2002; (b) The photograph was shot on July, 2008; the arrowhead shows the location of surface rupture, the
northern-western side of the rupture obviously uplifted relative to the photograph a.
Figure 9. Distribution map for the surface rupture of the Wenchuan Earthquake in Liulin village, Leigu town. (a) the unworked air-
scape; (b) the worked airscape; the black lines figure the distribution of the surface rupture, the black-sawtooth lines shows the hang-
ing wall of the rupture; V: vertical offset; H: horizontal offset.

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Figure 10. Displacements of the surface ruptures in the west of Leigu town. (a) the vertical displacements of the terrace I
and the water slot, the arrowhead shows the locate of the water slot; (b) the offset on the foundation of the house.
Figure 11. The surface rupture of the Wenchuan Earthquake in Maoba village, Beichuan county. (a) the vertical displacements
in Maoba village; (b) the vertical and horizontal displacements of the plat in the front of a building; (c) the right-lateral offset of
the field.
pathway in the village is about 2.5 m and the right-lateral
offset of it is 2.4 m. The terrace of the river, floodplain
and riverbed were incised by the rupture in the south-
west of the spot. The fractured zone of bedrock outcrops
near the bank of river. The vertical displacement of a
pathway on the floodplain is about 2.1 m and the right-
lateral of it is about 1.78 m (Figure 12(b)).
8) The surface rupture of the Wenchuan Earthquake in
Pingtong town
The surface rupture near the Pingtong town is about

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167
Figure 12. The surface ruptures of the Wenchuan Earthquake in Chenjiaba town and Fenghuang village, Guixi town.
(a). the displacement of the terrace Ⅰin Chenjiaba village; (b). the displacement of a pathway and the floodplain in
Fenghuang village, Guixi town.
Figure 13. Waterfall was created by the surface rupture of
the Wenchuan Earthquake in Pingtong town.
1km long and is N50-60°E trending. The road, river ter-
race and the river bed are offset by the rupture (Figure
13). The vertical displacement of the road is about 1.9 m.
All above facts indicated that the surface rupture on
the Beichuan-Yingxiu fault showed the thrust, dextral
slip characteristic of the fault. The maximum vertical
displacement of the surface rupture is about 6.5 m and
the maximum right-lateral displacement is about 5.85 m.
Though the vertical displacements and the horizontal
ones of the different segments have certain differences,
as a whole, the ratio of the vertical displacement and the
horizontal is close to 1:1. This is consistent with the pre-
vious studies [12].
2.2. The Surface Rupture on the
Pengxian-Guanxian Fault
The Pengxian-Guanxian fault is also called Pengguan
fault [5]. The Wenchuan Ms8.0 earthquake occurred on
12th May produced the coseismic surface rupture on this
fault. The surface rupture begins near Xiangê town, Du-
jiangyan city. It sketches to the northeast, passes through
Cifeng town in Pengzhou county，Bailu town，Jinhua
town in Mianzhu city, Hanwang town, and breaks off
near Sangzao town in Anxian county. The total length of
it is about 50 kilometers.
1) The surface rupture of the Wenchuan Earthquake in
Cifeng town
The southwest end of the surface rupture shows that
the fault thrust from the northwest to the southeast and
produced a reverse fault scarp. The rupture is N10-50°E
trending and shows a broad wave-like on the surface,
with the length of 200-300 m. The heights of the fault
scarps are between 0.24 m to 0.7 m. The displacements
of six ridges in the field are between 0.24 m to 0.5m
(Figure 14(a)). Here, the vertical displacements are
slightly larger than the horizontal ones.
2) The surface rupture of the Wenchuan Earthquake in
Bailu town
The surface rupture passes through between two
teaching buildings of the central school in Bailu town,
Pengzhou city. The height of the fault scarp is about 2 m.
According to measuring the length of superposition of
the mattess, the shortening amount is 1.65 m (Figure
14(b)). The ruptures primarily present the thrust charac-
teristic of the fault and the crustal shortening. It only
shows a little horizontal displacement. Several gaps of
the mattess are cut off and the maximum displacement is
0.42 m. Northeast about 300 m to this spot, the river bed
was cut off and produced a fault scarp with a height of
1.8 m (Figure 15(a)). The right-lateral offset of the bank
of the river is about 0.8 m (Figure 15(b)).
3) The surface rupture of the Wenchuan Earthquake in
Jinhua town.
The surface rupture is N65-70°E trending in Jinhua

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Figure 14. The surface rupture of the Wenchuan Earthquake in Cifeng town and Bailu central school. (a) the fault scarp and
the offset of ridges in a field; (b) the fault scarp on the playground in the Bailu central school.
Figure 15. The surface rupture of the Wenchuan Earthquake on the riverbed and bank of Bailu river. (a) the fault scarp and
waterfall on the riverbed was created by the Wenchuan Earthquake; (b) the right-lateral offset of the river bank.
Figure 16. The surface rupture of the Wenchuan Earthquake in Jinhua and Hanwang town, Mianzhu county. (a) Scraps of the
Penxian-Guanxian fault in Jinhua town; (b) Scraps of the Penxian-Guanxian fault in Hanwang town, the arrowheads show
the location of the surface rupture
town, Mianzhu city (Figure 16(a)). The vertical dis-
placement of the riverbed and terrace I is 1.5-2.0 m. The
right-lateral dislocation of the lateral edge of the terrace
I is 0.7 m. The scarps on the surface of the terrace III are
lower relatively and the heights of them are between 0.4 m
and 0.7 m. The dextral displacements of a pathway and

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169
the road are 0.18 m，0.5 m respectively.
4) The surface rupture of the Wenchuan Earthquake in
Hanwang town
The surface rupture is N48°E trending in the north of
Hanwang town, Mianzhu city (Figure 16(b)). The right-
lateral dislocation of the road in the east bank of the
Mianyuan River is 0.3-0.4 m. The vertical displacement
of a road in the west bank of the river is about 1.0 m and
the dextral dislocation is 0.4-0.6 m. The crustal shortening
is 1.3 m.
In a word, it believes that the surface rupture on the
Pengxian-Guanxian fault shows thrust and dextral char-
acteristic of the fault. The vertical displacements and the
horizontal ones on some segments are approximately
equal. But the rates of them on the most other segments
are between 1:3 and 1:2. The maximum horizontal
shortening is 1.65 m. All of these show that the main
characteristic of the fault rupture is thrust and shortening.
According to the surface rupture characteristic of the
Wenchuan Ms8.0 earthquake on the Beichuan-Yingxiu
fault and Pengxian-Guanxian fault, a seismogenic struc-
tures model of this earthquake can be made. The model
shows that the inclination of the Beichuan-Yingxiu fault
becomes flat gradually and disappears in the horizontal
detachment layer about 20 km deep under the surface at
last. The inclination of the Pengxian-Guanxian fault be-
comes flat too from the surface to the deep crust and
converges with the Beichuan-Yingxiu fault at last. The
collision of India-Asia Plate resulted in Sichuan-Qinghai
block slipped to the NEE orientation. The activity of the
Longmen Shan tectonic belt transformed brittle and
thrust-dextral motion, accumulating tectonic stress. The
hypocenter of the Wenchuan Ms8.0 earthquake is on the
section of the Beichuan-Yingxiu fault, where the section
of the fault up warped from the horizontal detachment
layer. It simultaneously made the Pengxian-Guanxian
fault produce coseismic dislocations (Figure 17).
3. HAZARD OF THE WENCHUAN Ms8.0
EARTHQUAKE
The primary hazard characteristics of the Wenchuan
earthquake Ms8.0 are described as follows. 1) The seis-
mic wave produced strong ground motion, destroying
the structures. While the earthquake occurred, the writers
were working in the seventh floor office in the urban
district of Chengdu city. I could felt the strong vibration
of the structure and the vibration lasted about two min-
utes. During this period, the vibration became weak ob-
viously for 3-5 seconds. According to the seismological
inversion for the spatiotemporal process of the earth-
quake’s rupture, the first strong vibration that I felt was
produced by the initial rupture of the fault near Yingxiu
town. The rupture of the fault near Beichuan town re-
sulted in the second strong vibration. 2) The earthquake
produced a 220 km long surface rupture on the Beichuan-
Yingxiu fault and a 50 km long one on the Pengxian-
Guanxian fault. The surface ruptures cut off the struc-
tures and all of the structures close to the surface rupture
zones almost broke down. The surface rupture zone pass
through the central of the Pingtong town and all of the
buildings in the rupture zone collapsed. The other struc-
tures with 30-50 m distance of the zone did not collapsed,
only were severely or moderately destroyed.
3)The strong ground motion and the dislocation of the
surface rupture resulted in the secondary geological haz-
ards, such as landslip, collapse, and so on. The hazards
pulled down or severely destroyed the structures. The
earthquake occurred in the Longmen Shan area. Espe-
cially, the Beichuan-Yingxiu fault is the boundary fault
between the higher modern geomorphology and the
lower. The difference of the topographic height is very
big. Thereby under the interaction of the strong ground
motion and the dislocation of the surface rupture, the
earthquake produced a large-area and large-scale land-
slide, collapse et al. in the high earthquake intensity re-
gions of the Longmen Shan area. On the one hand, the
landslides and collapse directly destroyed or buried large
numbers of houses. For example, half of the houses were
directly destroyed by the landslides. On the other hand,
they blocked up the rivers and produced tens of sag lakes.
Many croplands and houses were submerged. It formed
a large potential threat of the flood disaster to the down-
stream region.
According to the investigations of the Earthquake
Emergency Job Team of China Earthquake Administra-
tion, Seismological Bureaus of Gansu province, Shanxi
province and Chongqing, it also made reference to the
studies of InSAR and records of seismographs and re-
checked the earthquake intensity of some major severely
damaged regions. Basing on these studies, the isoseismal
line of the Wenchuan Ms8.0 earthquake was drew (Fig-
ure 18). The isoseismal line only shows the general de-
gree of the damages of this earthquake. And we did not
considered the effect of the aggravated damages caused
by the surface rupture.
1) XI intensity region: There are three XI intensity re-
gions, occurring in Yingxiu-Hongkou, Yuejia Shan-
Gaochuan and Xuanping-Beichuan area respectively.
They distribute in the Beichuan-Yingxiu fault zone and
its hanging wall. The total area of them is about 680 km2.
The houses almost broke down in this area. Especially,
the houses in the Yingxiu town and Beichuan county
were completely destroyed. Individually, the
un-collapsed houses were also severely destroyed. The
scale of the surface is large and its continuity is gener-
ally well. The displacements of many segments are more
than 3 meters. The earthquake resulted in multiple-site
collapses and landslides. These second dary geological
hazards walled up the rivers and produced the sag

R. J. Zhou et al. / Natural Science 2 (2010) 160-174
170
Figure 17. The seismogenic structures model of the Wenchuan Ms8.0 earthquake.
Figure 18. Isoseismal line of the Wenchuan Ms8.0 earthquake on 12th May, 2008.
lakes, such as Qingping sag lake and Tangjia Shan sag
lake in Beichuan county, and so on.
2) intensity region: The southwest part of the rⅩe-
gion begins in the southwest of the Yingxiu town. It
0
-10
-20km

R. J. Zhou et al. / Natural Science 2 (2010) 160-174
171
sketches to the northeast and ends at Shikanzi village,
Nanba town. The region includes the surface rupture ex-
tension of the Beichuan-Yingxiu fault. It distributes as a
narrow area with a N50°E-trending long axis. The total
area of the region is about 2520 km2. The houses in this
region were generally destroyed and most of them were
broken down. There are many huge landslides in this area.
3) intensity region: The region arises from SanjⅨi-
ang town and Shuimo town, north-eastward to Shuiguan
town, Fangshi town, south-eastward to Xicheng town,
Hanwang town and Xiaoba town. A intensity abnoⅨr-
mal region occurred in the intensity region near Ⅷthe
juncture area of Sichuan province, Gansu province and
Shaanxi province. This area of the intensity region Ⅷ
sums up to 4000 km2. Most of the houses in there were
severely destroyed and many of them collapsed. The
collapses and landslides can be seen everywhere.
4) intensity region: This region arises from WeⅧn-
jing river, Heba village; north-eastward to Yangpingguan
village; north-westward to Weimen village in Maoxian
town, Pingwu, Wenxian town; south-eastward to Juyuan
village, Mianzhu, Yanmen village in Jiange town. A Ⅷ
intensity abnormal region occurred in the Hanyuan co-
unty. The total area of the intensity region is 17800Ⅷ km2.
Most of the houses in this region were severely or mod-
erately destroyed, a little collapsed. The collapses and
landslides are common too, but the scale of them is rela-
tively small.
5) intensity region: This region arises from Dawei, Ⅶ
north-eastward to Taibai, Foping village, north-westward
to Shuangliusuo village in Heishui town, Zhenping town
in Songpan county, Jiuzhaigou, Lixian county; south-
eastward to Deyang, Mianyang, Guangyuan city. The
total area of this region is 68000 km2. Generally, the
houses in this region are slightly destroyed. Many of
them were moderately destroyed and a little were seri-
ously destroyed. Individually, some adobe houses col-
lapsed. There are some collapses and landslides in the
region, but the scale of them is small.
6) intensity region: This region arises from Xiaojin, Ⅵ
Tianquan village, north-eastward to Sanyuan, Shanyang
village; north-westward to Hongyuan, Lintao, Jingning,
Pingliang city; south-eastward to Jianwei town, Zigong,
Hechuan county, Pingchang county. The total area of this
region is 240000 km2. Most of the houses were slightly
destroyed and a little were moderately destroyed. Indi-
vidually, some adobe houses were severely destroyed.
The collapses and landslides are rare in distribution in
this area. Most of them are rolling stones or part of the
slopes collapsing.
In a word, the total intensity area above degree of Ⅵ
the Wenchuan earthquake is about 333000 km2. The
characteristics of the isoseismal line are described as
follows.
1) The high earthquake intensity line stretches to
N40-50°E along Longmen Shan tectonic belt. The rate
of the long axis and the minor is between 8:1 and 10:1.
Three intensity regions are isolated in distrⅪibution. It
presents a multipoint instantaneous characteristic of the
rupture.
2) According to the seismological inversion, the initial
rupture of the fault is near Yingxiu town and cracked
unilaterally north-eastward along Longmen Shan belt.
The isoseismal line decayed rapidly south-westward and
slowly norh-eastward. It is consistent with the unilateral
rupture process.
3) The isoseismal line of intensity region dⅥecayed
slowly to Sichuan basin, Hongyuan and Nuoergai county.
The reason may be that Sichuan basin is in the rigid
Yangtze Platform and seismic wave propagated diffi-
cultly. And the soft oil layer in the Hongyuan, Nuoergai
area increased the hazard.
4) , and intensity regions stretch to eastⅥⅦ Ⅷ-west
in the north of Sichuan province, Guansu province and
the south of Shaanxi province. The intensity of the
earthquake may be under the control of the regional ma-
jor faults.
4. DISCUSSIONS
1) It is generally believed that the Longmen Shan tec-
tonic belt is a deep fault and the boundary fault between
the Songpan-Garzê orogenic belt and the Yangtze Carton
[1,6,8]. But there are different opinions on the late Qua-
ternary activities of the Longmen Shan tectonic belt
among different scholars. Tang [24] believed that some
segments of the Longmen Shan tectonic belt were Holo-
cene active faults, while the other segments were early
Quaternary faults. Zhou [12] and Densmore [5] believed
that most segments of the belt were Holocene active
faults and Beichuan-Yingxiu fault was the major active
fault. The acquaintanceship change among the scholars
has been undergone for 15 years. The deeply incised to-
pography, flourish vegetations, farmland reclamation and
low slip rate of the fault make the field study and map-
ping more difficult and uncertain. Only a few clear active
tectonic landforms were found on the Longmen Shan
tectonic belt with length of 300 km. Even so, most sur-
face rupture of the Wenchuan earthquake outcropped
along the locations of active tectonic landform of the
Beichuan-Yingxiu fault found by the scholars before. The
surface rupture did not outcrop along the linear structure
discovered before near Xujiagou village, Longmen Shan
town, but outcropped in the northwest of the linear struc-
ture with distance of 0.5-1.0 km. Only a few seismic frac-
tures cut into a sag-ponding discovered before. It presents
the dextral slip characteristic of the secondary fault, dis-
tributing at an angle 5-10°with the major fault. This may
be relative to the strain partition of the complicated fault
combination. The outcrop of the surface rupture on the
Pengxian-Guanxian fault is more complicated. On the
1:200,000 regional geological map, there are several

R. J. Zhou et al. / Natural Science 2 (2010) 160-174
172
northwest-trending faults with different scales and lengths.
It is difficult to confirm which is the major fault of the
Pengxian-Guanxian fault. The surface rupture stretches
through Bailu town with about 7 km distance south-
eastward the fault, not outcropping along the Holocene
active fault in the Daiming temple in the Tongji town,
Pengzhou county. It is very difficult to confirm the activ-
ity of the fault in Bailu town before the occurrence of
earthquake. Therefore, the decision should be made cau-
tiously for the activity of the faults in such region. A few
phenomena of the geology and landform are important
evidences to confirm the activity of the whole fault.
2) We have known the activity of several major faults
of the Longmen Shan tectonic belt. Especially, Beichuan-
Yingxiu fault is a Holocene active fault. Only 2-3 tre-
nches in previous field work revealed the paleoearth-
quakes [3-5]. According to the historical data, only 3-4
earthquake events above Ms6.0 are recorded and the
maximum is the Wenchuan Ms6.5 earthquake in 1657.
These make us believe that the maximum potential mag-
nitude of the earthquakes on the fault is about Ms7.0.
Furthermore, the topographic responses of the active
faults almost concentrate on the middle-south segment
of the Longmen Shan tectonic belt. The historical strong
earthquakes and modern small-moderate earthquakes are
dense in a belt along this segment. The seismicities on
the middle-north segment are weak. The gradient zone of
the crustal thickness along the Longmen Shan tectonic
belt changes from NE to NNE near Beichuan county and
stretches along the east boundary of the Minshan block.
The topography and geomorphology relatively changed
there. Therefore, the boundary of the subsection of the
Longmen Shan tectonic belt is near Beichuan county
[25]. The surface rupture of the earthquake broke
through the limit of the fault subsection and stretched
north-eastward to 30-40 km. It teminated at Shikanzi
village, Nanba town. The earthquake not only produced
about 220 km long surface rupture on the Beichuan-Yingxiu
fault, but also about 50 km long one on the Pengxian-
Guanxian fault. Thus, we should fully consider the scale
of active faults on determination of the potential earth-
quake resource according to sections of active faults. We
can’t confirm the upper-limit magnitude of the potential
earthquake resource through increasing the magnitude of
the maximum historical earthquake. Furthermore, it
should be fully demonstrated that the boundary of fault
subsections could control the propagation of strong
earthquakes’ rupture permanently. And it should be rec-
ognized that several faults in the reverse or reverse-slip
tectonic circumstance would be likely to crack coinstan-
taneously in a strong earthquake. This should be consid-
ered for determination of the potential earthquake re-
source.
3) The unilateral multipoint instantaneous rupture of
the earthquake increased the hazards in the north of Si-
chuan province, Gansu province and the south of Shanxi
province. The intensity region attenuated slowly to Ⅵ
the Sichuan basin, Hongyuan and Nuoergai county. It
presents a special attenuation characteristic of strong
earthquake. According to ‘National Standard of the Peo-
ple’s Republic of China. Seismic ground motion pa-
rameter zonation map of China’ (GB18306-2001) [26],
the area where the surface rupture outcrop are all the
partitions of ground motion parameter 0.1gal. It is in-
compatible with the article of ‘National Standard of the
People’s Republic of China. Code for Seismic Design of
Buildings’ (GB50011-2001) [27]. In this article, it is
considered that the causative fault could be neglectable
in the earthquake intensity region under degree. This Ⅷ
is because the interval recurrence of the great earth-
quakes above Ms8.0 is beyond a thousand years or sev-
eral thousand years. And the peak acceleration of the
ground motion could not reach degree in 500yr inteⅧr-
val recurrence. Moreover according to the investigation
of this earthquake, the structures in the surface rupture
zone almost collapsed or severely destroyed. The other
structures with 30-50m distance of the zone did not col-
lapse (such as the structures in Hongkou, Jinhua, Ping-
tong town et al.). There is obvious difference in the cri-
terion (GB50011—2001) [27] that the preventing belt
should be 200m to the causative fault for the third class
buildings in the inteⅧnsity region. So, it is suggested to
cancel the criterion that didn’t consider preventing the
causative fault under intensity region. We should Ⅷ
mainly consider the Holocene active faults. The pre-
venting distance to the causative fault could be modified
basing on this earthquake and making reference to the
overseas great earthquakes’ datum.
4) According to the surface rupture characteristics of
the earthquake, the Beichuan-Yingxiu fault is a dex-
tral-slip and thrust fault and the vertical displacement on
it is equal to the horizontal. The Pengxian-Guanxian
fault is thrust fault with a little dextral-slip component.
The slip rates of the major faults of the Longmen Shan
tectonic belt are not accurate enough. And the pa-
leoearthquakes is not enough for the determination of the
upper-limit magnitude. According to the records of
‘Compilation of Historical Data of Earthquakes in
China’ (Edited by Xie [28]), there were eleven historical
earthquakes during May 934A.D. to April-May 953 A.D..
Among them, two earthquake caused serious destroy.
One occurred during Nov.16 to Dec.15, 942 A.D.. The
other occurred during Nov.7 to Dec.6, 951 A.D.. Con-
sidering the bad quality of dwellers’ houses at that time,
the damage caused by the two historical earthquakes
showed that the intensities reached Ⅵ— degree. It is Ⅶ
equivalent to the effect of Chengdu city caused by the
Wenchuan Ms 8.0 earthquake. Densmore [5] excavated a
trench in Xiling town with distance about 70-80km to
Chengdu city. The 14C ages constrain the timing of the
last paleoearthquake event to 860 ± 40 – 930 ± 40 yr
B.P.. The A.D. year is 1090 ± 40 – 1020 ± 40 yr. It is

R. J. Zhou et al. / Natural Science 2 (2010) 160-174
173
nearly equivalent to the historical earthquake as men-
tioned above. Does it imply that a great earthquake with
equivalent magnitude as the Wenchuan Ms8.0 earth-
quake occurred a thousand years ago? The Wenchuan
Ms8.0 earthquake provides an opportunity to solve these
questions. There is very important scientific and practi-
cal meaning for the seismic risk assessment of the
Longmen Shan tectonic belt and its adjacent areas and
the earthquake disaster prevention of Chengdu Plain
with a large population density.
5. ACKNOWLEDGMENT
We are very grateful to the people who provided us supports and help.
Finally, we thank the people of the Longmen Shan region for their
unending curiosity, hospitality, and generosity.
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