10th Asian Regional Conference of IAEG (2015)

Seismic monitoring of Kangding Ms6.3 earthquake on the slope response

Wang Yunsheng(1), He Jianxian(2), Luo Yonghong(1), Cao Shuihe(2), He Zihao(2)(1) State Key Lab. of Geo-Hazard Prevention and Geo-Environment Protection,
Chengdu University of Technology, China(2) College of Environment and Civil Engineering, Chengdu University of Technology, China
Abstract
Some earthquakes whose magnitude is lower than Ms 7.0 induced strong secondary geohazards
such as Ludian earthquake of Yunnan in 2014 and Qianjiang earthquake of Chongqing in 1856,
topographic amplification is considered to be the main factor for the slope failure. However, up tonow, seismic monitoring data are not enough to support the idea. Kangding Ms 6.3 earthquake on
November 22, 2014 was monitored in Lengzhuguan section，Sichuan，China. Six monitoring
instruments in the slope adits were triggered by the earthquake. The data reveals: (1) comparedwith the valley bottom reference point of Guza station, the horizontal PGA amplification factorsof #1 station at the top of the ridge on the right bank is 10.6-11.5, and the vertical one is 7.1; andthe Arias Intensity is also significantly stronger; the horizontal PGA amplification factor of #2
station at the middle part on the right bank is 4.3-5.0, and the vertical one is 2.3; (2) the PGA
amplification factors of the stations on the left bank are smaller than those of the right bank andonly PGA amplification factor at the slope break is higher: the horizontal PGA amplification
factor of #5 at the slope break is higher, from 3.0-4.5, and the vertical one is 2.3, the horizontal
PGA amplification factor of #6 range from 1.9 to 2.1, and the vertical one is 1.7; (3) the outer part
PGA amplification factor of #7 station is larger than that of the inner part; (4) Horizontal tovertical spectral ratio illustrates that the #1 station on the right topographic amplification factor ofhorizontal component reaches 11.1, and Predominant period is concentrated in the low-frequency
on the right bank; while there are several Predominant period on the left bank and theamplification effect is more prominent at high-frequency.
Key words: Kangding Ms6.3 earthquake, topography amplification effect, Lengzhuguan section,slope seismic response
1. Introduction
Since last century, based on geological survey on
the slope seismic response and theoretical model
calculation, scholars at home and abroad have foundthat there are topographic amplification effects at
protruding topography, slope break and butte understrong earthquake, where more slope failures happened
than other parts of the slope on the whole. The seismic
response data analysis of Central Chile earthquake in1985 revealed that the frequency range of groundmotion amplification can be obtained by the frequency
ratio method and the amplification effects was obvious
at special geological site and mountain ridge (Celebi,1987). Geli (1988) revealed the topographic
amplification effects are obvious at the top of the hillwhere slope width is approximately equal to theincident wavelength; incident P-wave topographic

1

amplification effect is lower than the incident S-wave;
P-SV wave topographic amplification effect is slightly
stronger than the SH wave; and topographic
amplification effect would increase while the adjacentridges exist. The mountain hazard survey of Wenchuan
earthquake revealed that (Luo et al., 2013): thehorizontal components of the seismic waves can besignificantly enlarged by coupling of the terrain size
and the seismic wavelength, and the amplification
effect is distinct at the thin mountain ridge or bar
mountain, the part of slope break, convexity slope. It
can be concluded from Lushan earthquake mountainhazards (Huang et al., 2013): the source of rock fall is at
upper part of the steep slope and prominent spur.
Analysis of the Lengzhuguan slope of Lushan
earthquake seismic response revealed that groundmotion topographic amplification effect at thin ridge ofthe right bank was significantly stronger than the leftbank of the alpine slopes (Luo et al., 2013). The higher

10th Asian Regional Conference of IAEG (2015)

peak ground acceleration records in Wenchuan
earthquake were caused by the local topographic effects(Wen et al., 2013). Qi et al. (2007) simulated
three-components of acceleration distribution. Based on
surveying lots of secondary natural geological disasters
caused by Lushan (2013) and Ludian (2014) earthquake(both magnitude were not high), some scholars thought
it might be associated with topographic amplification
effects, but it was still lack of a large number ofmonitoring data on the slope seismic response.
With the support of China Geological Survey
Bureau(12120113009700),
National
ScienceFoundation of China (41072231), we set up a
monitoring section in Lengzhuguan in 2011. At 16:55
of November 22th, 2014, a magnitude Ms 6.3
earthquake occurred in the Kangding County, Sichuan,
China. The six seismic instruments were triggered in
the section, a series of data reveals the topographic
amplification discipline.

The distances between the Kangding Ms 6.3
earthquake epicenter and the monitoring site is about
56km and the depth of hypocenter is 18 kilometers, andsix strong monitoring instruments were triggered in theevent. The parameters of the monitoring stations areshown in Table 1, and the waveform of monitoring
stations (see Fig. 2) and the ground motion parametercharacteristics of each monitoring station are listed inTable 2.

2. Summary of the monitoring profile
Lengzhuguan earthquake monitoring section is
located in both sides of Lengzhuguan valley where thevalley meets the Dadu River and the section is on theright bank of the Dadu River (Fig. 1). Seven stations are
set in the section where two stations are on the rightbank and five stations are on the left bank ofLengzhuguan valley. One seismic monitoring
instrument is set in each station (the first to sixth
station), and two monitoring instruments are set in theseventh station (outer is 57m from the portal and inneris 135m from the portal). The E-catcher strong motion
seismographs made by Application of Japan earthquake
measuring strain, and the basic parameters are
sensitivity is 1V/G, metre full scale is
2000gal(1gal=1cm·s-2), and the range of cycle
frequency is DC~20Hz(-3dB).
3. Slope seismic response in Lengzhuguan section

Fig. 1 The plane distribution map of Lenzhuguan slope
seismic monitoring station
Table 1 The parameters of the monitoring stations
Number ofElevation

monitoring(m)stations

Epicentral

HorizontalTypedistance

depths toof bed(km)

portal(m)

rock

#

1

1516

56.25638

granite

#

2

1478

56.2331

1

granite

#

5

1518

56.0337

7

granite

#

6

1520

55.9515

10

granite7(Outer)

1686

55.718957

granite#1686

55.7189135

granite#7(Inner)Table 2 The ground motion parameter characteristics of the monitoring stations
Number of

Arias intensity

PGA/(gal)monitoring

Dominant frequency-1/(cm·s )/Hzstations

EW

SN

UD

EW

SN

UD

EW

SN

UD

#

1

188.1

147.6

111.8

24.7

25.5

6.0

2.04

2.54

5.07

#

2

70.4

69.9

36.5

2.4

2.3

0.6

2.04

2.04

5.31

#

5

49.9

62.4

36.6

1.7

1.6

0.8

4.42

3.31

9.29

#

6

35

26.4

27.6

0.5

0.3

0.3

1.24

1.01

8.59

7(Outer)

24.9

22.7

14.0

0.3

0.3

0.2

1.26

1.02

1.19

#

22.5

19.8

12.0

0.3

0.3

0.1

1.24

1.01

1.17

#

7(Inner)2

10th Asian Regional Conference of IAEG (2015)

200

30

40

50

60

SN, PGA:147.6gal

100
0
-100
-200
2000

10

20

100

30

40

50

60

UD, PGA:111.8gal

0

-40

-40

-80
80 0

10

20

30

40

50

60

SN, PGA:69.9gal

40
0
-40
-80
800

10

20

30

40

40

50

60

-80
80 0

0

0
-40

-80

-80

20

30

Time/s40

50

60

a. waveform of #1 station

10

20

30

Time/s40

50

60

b. waveform of #2 station

EW, PGA:35gal

20

30

40

50

60

SN, PGA:26.4gal

20
0
-20
-40
400

10

20

20

30

40

50

60

UD, PGA:27.6gal

10

20

30

40

50

60

SN, PGA:22.7gal

15
0
-15
-30
300

10

20

15

30

40

50

60

40

50

d. waveform of #6 station

60

-30

60

30

Time/s

40

50

60

EW, PGA:22.5gal

0

10

20

30

Time/s

40

10

20

50

60

e. waveform of #7 station(outer)

30

40

50

60

50

60

50

60

SN, PGA:19.8gal

-30
300
0

30

20

10

20

15

UD, PGA:14.0gal-15Time/s

50

0

0

20

40

-15

-15

10

10

15

0

0

0

-30
30 0

-20
-40

30

UD, PGA:36.6gal

-15

-30
30 0

Acceleration/(cm•s-2)

20

Acceleration/(cm•s-2)

10

20

0

-15

-40
40 0

10

15

0

-20

60

30

EW, PGA:24.9gal

15

0

50

c. waveform of #5 station

30

40

Acceleration/(cm•s-2)

0

40

0

40

UD, PGA:36.5gal

30

SN, PGA:62.4gal

-80
800

-40

10

20

-40

0

0

10

40

-100
-200

EW, PGA:49.9gal

400Acceleration/(cm•s-2)

20

Acceleration/(cm•s-2)

Acceleration/(cm•s-2)

-100
10

EW, PGA:70.4gal

40

0
-200
200 0

80

80

EW, PGA:188.1gal

100

-30

30

40

UD, PGA:12.0gal

0

10

20

30

Time/s40

f. waveform of #7 station(inner)

Fig. 2 The acceleration waveform of monitoring stations
According to the seismic data of #1, #2, #5, #6 stationand the outside and inside of #7 station, the horizontal
and vertical component PGA of #1 station is 188.1gal
and 111.8gal respectively, and the horizontal andvertical component PGA of inside monitoring
instrument of #7 station are 22.5gal and 12.0gal
respectively. The horizontal and vertical component
PGA of #5 station is 62.4gal and 36.6gal on the leftbank. The data reveals that the PGA on the right bank is
about three times as those on the left. The PGA of theoutside of #7 station (57m from the adit portal)
monitoring station is larger than the inside (135m fromthe adit portal).
Site response directivity can be effectively analyzed
by examining directional variation of Arias intensity(Arias, 1970). The Arias intensity (Ia) in three
directions of each monitoring station are shown in
Table 2, from which the horizontal and vertical Ia of #1
station are 25.5 and 6.0cm/s, and the horizontal andvertical Ia of #5 station are 1.7 and 0.8cm/s on the leftbank. The maximum horizontal Ia on right bank is
about 15 times as much as that on the left bank and thevertical Ia is about 7.5 times. We can also find that thehorizontal and vertical Ia of #1 are about 2.7 and 3.1
times as much as that of #2 on the right bank, and the #6
are about 1.4 and 2.0 times as much as that of #7, andthe outer and inner Ia of #7 is at the same level.
Therefore, the seismic energy of the right bank isstronger than that of the left bank.
Table 2 reveals the horizontal predominant3

frequency of #1 and #2 station on the right bank is about
2.04 to 2.54 Hz and the vertical is 5.07 to 5.31 Hz. And
the EW predominant frequency of #5 station is 4.42 Hz,
SN is 3.31 Hz, and the vertical is 9.29 Hz. The EW and
SN predominant frequency of #6 station are 1.24 and1.01 Hz, and the vertical is about 8.59 Hz. The outerand inner predominant frequencies of #7 monitoring
station are same: the east to west predominantfrequency is 1.24 Hz, south to north is 1.01 Hz, and thevertical is 1.17 Hz.
4. The acceleration response spectrum
The concept of the response spectrum was carriedout based on Elastic system dynamics (M. A. Biot,
1941). Later a series of response spectrum curve wereobtained by some typical strong earthquake
accelerations (G.W.Housner, 1959). Response spectrum
is defined as the relationship between absolute value ofthe maximum response with cycle which is at the same
damping ratio of a series of single degree of freedom
system, and its essence is the reaction of ground motion
characteristics. According to Chinese Specification ofStrong Motion Safety Monitoring for Hydraulic
Structures (DL/T 5416-2009), the horizontal andvertical acceleration response spectrum which are indifferent damping ratio (for 0.05, 0.1, 0.2) arecalculated (see Fig. 3).

10th Asian Regional Conference of IAEG (2015)

700

500
400
300
200
100
0

0

1

2

3

500
400
300
200
100
0

4

500

SN response spectrum of #1 station

600

Acceleration amplitude/(cm•s-2)

EW response spectrum of #1 station

600

Acceleration amplitude/(cm•s-2)

Acceleration amplitude/(cm•s-2)

700

0

1

2

3

Vertical response spectrum of #1 station

400
300
200
100
0

4

0

1

2

3

4

Time/sTime/sTime/sa. the acceleration response spectrum of #1 station
160
140
120
100
80
60
40
20
0

0

1

2

3

4

240
220
200
180
160
140
120
100
80
60
40
20
0

100

SN response spectrum of #2 station

0

1

2

Time/s3

Acceleration amplitude/(cm•s-2)

EW response spectrum of #2 station180

Acceleration amplitude/(cm•s-2)

Acceleration amplitude/(cm•s-2)

200

Vertical response spectrum of #2 station

90
80
70
60
50
40
30
20
10
0

4

0

1

Time/s2

3

4Time/sb. the acceleration response spectrum of #2 station

120
100
80
60
40
20
0

0

1

2

3

160

180

SN response spectrum of #5 station160

Acceleration amplitude/(cm•s-2)

EW response spectrum of #5 station

140

Acceleration amplitude/(cm•s-2)

Acceleration amplitude/(cm•s-2)

160

140
120
100
80
60
40
20
0

4

0

1

2

3

Vertical response spectrum of #5 station

140
120
100
80
60
40
20
0

4

0

1

Time/sTime/s2

3

4Time/sc. the acceleration response spectrum of #5 station
EW response spectrum of #6 station

90
80
70
60
50
40
30
20
10
0

0

1

2

3

130
120
110
100
90
80
70
60
50
40
30
20
10
0

4

60

SN response spectrum of #6 station

0

1

2

3

Acceleration amplitude/(cm•s-2)

Acceleration amplitude/(cm•s-2)

Acceleration amplitude/(cm•s-2)

100

40
30
20
10
0

4

Vertical response spectrum of #6 station

50

0

1

Time/sTime/s2

3

4Time/sd. the acceleration response spectrum of #6 station

40
30
20
10
0

1

2

3

50
40
30
20
10
0

4

SN response spectrum of#7 station(outer)60

Acceleration amplitude/(cm•s-2)

50

0

50

70

EW response spectrum of#7 station(outer)60

Acceleration amplitude/(cm•s-2)

Acceleration amplitude/(cm•s-2)

70

0

1

2

Time/s

3

30
20
10
0

4

Vertical response spectrum of#7 station(outer)

40

0

1

2

3

4

Time/sTime/se. the acceleration response spectrum of #7 station(outer )
50

40
30
20
10
0

0

1

2

3

4

40

SN response spectrum of#7 station(inner)

40

Acceleration amplitude/(cm•s-2)

EW response spectrum of#7station(inner)

50

Acceleration amplitude/(cm•s-2)

Acceleration amplitude/(cm•s-2)

60

30
20
10
0

0

1

2

Time/s3

4

Vertical response spectrum of#7station(inner)

30

20

10

0

0

1

2

3

Time/sTime/sf. the acceleration response spectrum of #7 station(inner)
Damping ratio of 5%,

Damping ratio of 10%,

Damping ratio of 20%

Fig. 3 The acceleration response spectrum of monitoring stations

44

10th Asian Regional Conference of IAEG (2015)of #6 is about 2.1 and the vertical is merely 1.7; theouter and inner horizontal PGA amplification
coefficient of #7 station is between 1.3 and 1.6,
however the vertical PGA magnification coefficient isdecreased partly. So the PGA amplification on the rightbank is much larger than the left, and the #1 is larger
than #2 station on the right bank, and the #5 is larger
than #6 and #7 station on the left bank.

The acceleration amplitude decreased with theincreasing of damping ratio, and the acceleration
amplitude is at the largest with the damping ratio of
0.05. The ups and downs of horizontal or verticalacceleration response spectrum curve of eachmonitoring point are more consistent, i.e., obtaining theacceleration amplitude in different damping ratio at thesame time. The results show that the seismic amplitude
value is affected by the damping characteristics ofground while the process of ground motion
characteristics is not affected obviously. The horizontal
acceleration amplitude of each monitoring point isbigger than the vertical with various damping ratio
which is consistent with the waveform of monitoring
stations. Compared with the acceleration response
spectrum curve of #1 and #2 station on the right bank,the horizontal acceleration amplitude of #1is about 3.1
times as the #2 station with the same damping ratio, andthe vertical is up to 4.5. What’s more, the acceleration
amplitude of #1 station with the damping ratio of 0.2 isalso bigger than the #2 station which damping ratio is0.05, which is also bigger than each monitoring
stations on the left bank with the damping ratio of 0.05.
So the acceleration amplitude of response spectrum on
the right bank is bigger than that on the left bank.

6. Conclusion
Reference to Guza station of the main shock recordof Kangding Ms6.3 earthquake (its horizontal andvertical component PGA was16.4 and 15.7gal), themonitoring data on the two bank of Lengzhuguan
section reveals obvious topography amplification
effects: (1) the horizontal and vertical PGA
amplification coefficients of #1 station which is on the
top of the peninsular terrain on the right bank reach
10.6-11.5 and 7.1; (2)#2 monitoring station is 4.3-5.0
and 2.3; (3)the horizontal and vertical PGA
amplification coefficients of #5 station which is on theleft nearly linear slope is 3.0-4.5 and 2.3; (4) #6 stationis 1.9-2.1 and 1.7; (5)horizontal PGA amplification
coefficients of #7 station is1.46-1.6.

5. Topography amplification effectAcknowledgements

Reference to Guza strong earthquake monitoring
station of the main shock records (its horizontal andvertical component PGA was16.4 and 15.7gal) which
is about 7 km apart from the Lengzhuguan monitoring
section, the PGA amplification coefficients of eachmonitoring stations are shown on the Fig. 4.

This study is financially supported by the National
Foundation for Natural Science of China (41072231)
and the foundation of China Geological Survey(12120113009700).
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Vertical magnification coefficent

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EW magnification coefficent[1] Celebi. Topographic and geological amplification
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SN magnification coefficent

64reference station
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#

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7(outer) 7(inner)

Number of monitoring stations

Fig. 4 The PGA response coefficient ofeach monitoring station
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magnification coefficient is 7.1, while both of #2
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