Vol. 45 No. 3
SCIENCE IN CHINA (Series D)
March 2002
On crustal movement in Mt. Qomolangma area
CHEN Junyong ()1, WANG Zemin ()2, PANG Shangyi ()1,
ZHANG Ji (
)1 & ZHANG Quande (
)1
1. State Bureau of Surveying & Mapping, Beijing 100830, China;
2. Wuhan Technical University of Surveying & Mapping, Wuhan 430079, China
Correspondence should be addressed to Chen Junyong (email: [email protected])
Received March 20, 2001
Abstract Mt. Qomolangma lies in the collision zone between the fringe of Eurasia plate and Indian plate. The crustal movement there is still very active so far. In the past three decades China
carried out five geodetic campaigns in Mt. Qomolangma and its north vicinal area, independently
or cooperatively with other countries, including triangulation, leveling, GPS positioning, atmospheric, astronomical and gravity measurements. On the basis of the observation results achieved
in the campaigns the crustal movements in the area were studied and explored. A non-stationary
phenomenon both in time and space of the crustal vertical movement in the area is found. There
seems to be some relevance between the phenomenon of non-stationary in time and seismic episode in China. The phenomenon of non-stationary in space is possibly relevant to the no-homogeneity of crustal medium and non-uniform absorption of terrestrial stress. The horizontal crustal
movement in the area is in the direction of NEE at a speed of 6ü7 cm per year, and the trend of
strike slip movement is manifested evidently in the collision fringe of Indian plate and Qinghai-Xizang block.
Keywords: Mt. Qomolangma, crustal movement, geodynamics.
Mt. Qomolangma (MQ for short hereafter) is the highest mountain in the world. It lies between the boundary of China and Nepal, and also in the compressed collision zone between the
fringe of Eurasia and Indian plates. The crustal movement in MQ and its north vicinal area (MQ
area for short hereafter) is still very active so far. As part of the geo-science study on the Tibetan
Plateau, five geodetic campaigns and the corresponding study in the MQ area were conducted by
China independently or cooperatively with other countries in 1966, 1975, 1992, 1998 and 1999
respectively in the past three decades. Triangulation, leveling, GPS positioning, astronomical,
gravity and atmospheric refraction measurements were carried out in the campaigns. Crustal
movement in the MQ area has been studied on the basis of the observation results achieved in the
ü
campaigns[1 5].
1
Crustal vertical movement in the MQ area
The National 1st or 2nd order bench mark in a range of 70 km in the north from the MQ was
usually taken as the initial point for the leveling in the MQ area. In 1966 and 1975[1] the leveling
control measurement in the MQ area was started from the National 1st order bench mark
234
SCIENCE IN CHINA (Series D)
Vol. 45
Dingjiang 3, and conducted along the 2nd Dingrong leveling line (fig. 1) located in the west part
of the MQ area. For the elevation changes at the bench marks along the Dingrong leveling line
from 1966 to 1975, refer to table 1and fig. 2.
Fig. 1. Sketch map for the geodetic campaign (1966) in the MQ area.
As the roads along the Dingrong leveling line were destroyed after 1975, the leveling control measurements in the MQ area
in 1992 and 1998 were started from the national 2nd order bench mark IISala58, and
conducted along the 2nd Bangrong leveling
line (fig. 3) located in the east part of the
MQ area. For the elevation changes at the
bench marks along the Bangrong leveling
line from 1992 to 1998, refer to table 2and
Table 1 Elevation changes at bench marks of Dingrong leveling
line in the MQ area (1975—1966)a),b)
Point
Elevation change/mm
Distance to MQ/km
I Dingjiang 3
0
68
Dingrong 1
0
64
Dingrong 2
13
60
Dingrong 3
24
46
Dingrong 4
30
38
Dingrong 5
15
32
Dingrong 6
31
26
Dingrong 7
29
22
Dingrong 8
9
20
Dingrong 9
8
18
a) Elevation changes are referred to I Dingjiang 3 point.
b) Vertical datum system is China Yellow Sea 56.
No. 3
ON CRUSTAL MOVEMENT IN Mt. QOMOLANGMA AREA
235
fig. 4. The accuracy of the leveling control measurement mentioned above was executed according to the National Standard for the 2nd order leveling measurement[6].
Fig. 2. Crustal vertical movement in the MQ area (1975k1966).
Fig. 3. Sketch map for the geodetic campaign (1992) in the MQ area.
236
SCIENCE IN CHINA (Series D)
Tables 1 and 2 and figs. 2 and 4 show
the achievements of leveling control measurements in different years at 70 km’s
scope in the MQ area. From these data
and figures it can be found that there is a
wavering undulation in the relative vertical crustal movement in the area. It seems
that driven by Indian plate the elevations
of leveling points in the MQ area are accompanied by wavering undulation in a
relatively short period on the background
of the long period of crustal uplift in Tibet.
The magnitudes of undulation and degrees
of propulsive force are likely to be closely
related to the physical property of the
crust in the MQ area.
Vol. 45
Table 2 Elevation changes at bench marks of Bangrong leveling line
in the MQ area (1998—1992)a),b)
Point
Sala 58
Elevation change/mm
0
Distance to MQ/km
67
Bangrong 01
−1
64
Bangrong 02
−4
61
Bangrong 03
−3
59
Bangrong 04
−11
58
Bangrong 05
−3
56
Bangrong 11
+7
42
Bangrong 13
+5
36
Bangrong 14
+9
35
Bangrong 15
+15
33
Bangrong 18
+12
23
Branch 1
Fuducial Point of MQ
+10
20
−2
+11
16
12
Branch 1
a) Elevation changes are referred toSala 58 point. (b) Vertical
datum system is China Yellow Sea 85.
Fig. 4. Crustal vertical movement in the MQ area (1998k1992).
2
Crustal vertical movement and seismic episode in the MQ area
Bench mark Bangrong 15 (see table 2, the same point but in another name Dingrong 7 in
table 1) and Branch 1 are the only two coincident points in the leveling in 1966, 1975, 1992
and 1998 leveling measurements. They are located respectively at distances of 33 and 20 km to
the north of MQ. The elevation changes at the two points may typically demonstrate the relative
crustal vertical movement and its rate in the MQ area (tables 3 and 4, fig. 5).
The average annual rates (in different periods) of crustal vertical movement in the MQ area
are listed in table 4. It is on the basis of leveling data at bench mark Bangrong 15 and Branch 1. The data show that the rates of elevation change are not uniform and constant. It seems
that on the long-term background of pulsation upheaval[7] there is also some pulsation upheaval in
No. 3
ON CRUSTAL MOVEMENT IN Mt. QOMOLANGMA AREA
237
short term.
Table 3 Elevation at coincident leveling points in various years in the MQ areaa)
Point
Bangrong 15
(Dingrong 7)
Branch 1
(unit: meter)
Leveling in
1966
Leveling in
1975
Leveling in
1992
Leveling in
1998
Distance to MQ/km
4701.464
4701.493
4701.570
4701.585
33
5005.942
5005.952
20
5005.854
a) Vertical datum system is China Yellow Sea 85.
Table 4 Crustal vertical movement rate at bench mark in the MQ area
Interval between measurements
19751966
19921975
Average annual rate of elevation
3.0
4.3
change/mm
Seismic status in China
Seismically active episode
Seismically quiet episode
19981992
2.2
Seismically active episode
The comparison of crustal vertical movement in the MQ area with China’s seismic episode[8]
in the same period are also listed in table 4. It can be found that a seismically active period corresponds with the relatively low rate and a seismically quiet period with the relatively high rate. The
mechanism may be as follows. (i) If the rate of crustal vertical movement is high, the propulsive
force from Indian plate is largely absorbed by the deformation of the Qinghai-Xizang block’s
border; moreover, the crustal deformation weakens the transmission of stress; therefore, there
were few earthquakes in this period. (ii) If the rate is low, stress is absorbed to a small extend and
it transmits farther, thus making the country’s seismic zone active, and more earthquakes occur.
Contrary to the crustal uplift in the north of MQ, the observation results at GPS monitoring
points in the south (South Col) of MQ show that there was merely 3 mm’s crustal uplift at that
point, and the rate was only 0.8 mm/a. It seems that the vertical crustal movement in the south is
very faint; therefore, an interpretation is allowed that the pressing force of collision from the Indian plate is largely released in the Tibetan area through the edges of Indian and Eurasia plates. Of
course it is not adequate to draw an affirmative conclusion according to the above-mentioned
phenomena and the mechanism in view of geodesy, only one branch of geosciences. However,
these data or facts here may be valuable to other branches of geosciences for further study.
3
The crustal horizontal movement in the MQ area
The amounts of crustal horizontal movement at coincident points in the MQ area, according
to GPS observations in 1992 and 1998, are listed in table 5.
Table 5 Crustal horizontal movement at GPS points in the MQ area
Point
Quzong (14)
Fiducial point of MQ
7
West 1
Dingjiang 1
Dingjiang 6
Dingjiang 2
Jilong (4)
Piramid
B
28
28
28
28
28
28
28
28
27
19
08
06
04
35
37
30
16
58
L
86 51
86 51
86 52
86 51
86 37
87 10
86 37
86 49
86 49
∆B
(19981992)
0.0081
0.0081
0.0081
0.0079
0.0071
0.0079
0.0079
0.0081
0.0085
∆L
(19981992)
0.0106
0.0103
0.0103
0.0107
0.0112
0.0109
0.0108
0.0106
-0.0048
238
SCIENCE IN CHINA (Series D)
Vol. 45
Figs. 5 and 6 show the rates of horizontal movement drawn from the amounts of horizontal
movement at GPS points in the MQ area.
Fig. 5. Speed field for crustal horizontal movement in the
MQ area (relative to the ITRF96 frame).
Fig. 6. Speed field for crustal horizontal movement in the
MQ area (relative to Eurasia plate).
The dotted lines in figs. 5 and 6 are roughly corresponding to the boundary between the Indian plate and the Eurasia plate. It can be seen plainly that driven by the Indian plate the MQ area
moves in the direction of north-east-east (azimuth 54°, 67 cm/a). The Eurasia northward shifting speed was found simultaneously at GPS monitoring points in both sides of the MQ, while the
trend of strike-slip movement was obviously shown in east-western direction, so we can infer that
a large-scale strike-slip fracture may exist beneath the MQ. Naturally, the MQ area is quite a small
part of the collision fringe of the two plates, it may not represent the general state of the two
plates’ movement. However, the strike-slip movement of the two plates is found partially or
wholly according to the GPS observations (fig. 7) in the paper. The strike-slip movement may be
caused by the non-normal intersecting between the contact surface and the direction of the propulsive force of the two plates.
4 Field of terrestrial strain rate in the MQ area
Corresponding parameters of terrestrial strain rate can be obtained (see table 6 and fig. 7)[9]
on the basis of the speed field of crustal horizontal movement (figs. 5 and 6).
Among parameters of strain field according to the crustal horizontal movement determined
by GPS measurement, when the pyramid point was taken into consideration, the maximum tensile
strain rate determined by triangle is 3.9710−7/a and in the direction of north by 170° west; the
maximum compressive strain rate is −2.010−7/a, north by 3° east; while the maximum chief
strain rate of block (tensile strain rate ) determined by ten points is 3.710−9/a, north by 49°west;
the minimum principal strain rate (compressive strain rate) is −6.610−9/a, north by 41° east.
When pyramid point was not taken into consideration, the maximum tensile strain rate determined
by triangle is 0.110−8/a, in the direction of north by 66° west; the maximum compressive strain
No. 3
ON CRUSTAL MOVEMENT IN Mt. QOMOLANGMA AREA
239
rate is −0.910−8/a, north by 27° east; while the maximum principal strain rate of block (tensile
strain rate ) is 3.010−10/a, north by 46° west; the minimum chief strain rate (compressive strain
rate) is −1.710−9/a, north by 44° east. For detailed strain in the MQ area, refer to table 6 and
fig. 7.
Fig. 7. Strain rate field determined by crustal horizontal movement. (a) Including pyramid point. (b) Excluding pyramid point.
Table 6 Parameters of strain rate field determined by crustal horizontal movement in the MQ area
Parameters of strain rate field
Maximum principal strain rate ε 1
(0.01 µstrain/a)
Minimum principal strain rate ε 2
(0.01 µstrain/a)
Maximum principal strain rate azimuth
α1/ ()
Maximum rate of shearing strain γ m
(0.01 µstrain/a)
Rate of superficial expansion ∆ (0.01 µstrain/a)
γ 1 (0.01 µstrain/a)
γ2 (0.01 µstrain/a)
Mt. Qomolangma (19981992)
including pyramid point
excluding pyramid point
0.37284
0.03037
−0.65558
−0.17034
131.774
134.130
1.02842
0.20071
−0.28274
−0.11555
−1.02191
−0.13997
−0.00610
−0.20062
a) 1 µstrain = 1 ppm = 1.010−6.
It can be seen from the GPS long time monitoring observations (table 6 and fig. 7) that in the
background of compression in the direction of NE-SW, there also exists stretching in the direction
of NW-SE. The macro-state of topography and geography in the MQ area also reflects the results
by the stress applied. Since MQ is situated in the boundary belt of compression and under-thrust
between the Indian plate and the Qinghai-Xizang block, tremendous elevation change in topography of the MQ area is made by the very strong compression in the NE-SW direction in the area.
240
SCIENCE IN CHINA (Series D)
Vol. 45
For example, mountainous topographic height from 7000 to 8000 m dropping suddenly to 5000ü
6000 m in the NE direction within a scope of 20ü30 km. However, it was found that the displacement of GPS monitoring points on the two sides of the collision edge of the two plates is
sometimes in opposite direction or with different rates in the SW direction. So another geographic
feature of the MQ area is that there are many glaciers in column direction, such as the East
Rongbu glacier, the Middle Rongbu glacier and the West Rongbu glacier. The forming of this
geographic phenomenon is not only affected by the washout of water, ice and snow, but also the
stretching in the NW-SW direction.
5 Summary
(i) According to the analysis of the results obtained in geodetic campaigns in the past three
decades, it is known that there exists non-stationaryüüin time and space of ten years’ magnitude
üü crustal vertical movement in the MQ area. (ii) The non-stationary in time for the crustal vertical movement in the MQ area seems relevant to some extent to the seismic episode. (iii) The
non-stationary in space for crustal vertical movement in the MQ area is likely related to the
non-homogeneity of crustal medium and non-uniform absorption of terrestrial stress. (iv) According to precise GPS measurements obtained in 1992 and 1998, respectively, crustal horizontal
movement in the MQ area is found at the speed of 6ü7 cm per year in the direction of
north-east-east (azimuth 54°). (v) The results of GPS measurement indicate that on evident
strike-slip movement is shown in the collision fringe between the Indian plate and the Qinghai-Xizang block.
Acknowledgements Thanks to the hard work of mountaineers and geodesists, who joined the geodetic campaigns in the
MQ area in the past three decades, all the discussions in the present paper then can be made. Sincere appreciation is extended to
them from the authors. In addition, relevant departments of the State Bureau of Surveying and Mapping as well as academicians
Ye Shuhua and Ma Zongjin who energetically supported the project are also sincerely acknowledged. This work was supported
by the Science Fund of the State Bureau of Surveying and Mapping (Grant No. C95-04) and the National Climbing Project of
China (Grant No. 970231003).
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
Zhu Liang, The height determination of Mt. Qomolangma, Science in China (in Chinese), 1976, (1): 7477.
Chen Junyong, Liu Yongruo, Zhang Ji et al., Determination of gravity field in boundary belt between Indian and Eruasia
Plates, Acta Geodaetica et Cartographica Sinica (in Chinese), 1994, 23(4): 241265..
Chen Junyong, Liu Yongruo, Zhang Ji et al., On crustal movement, crustal thickness, tensional glacier in the Mt. Qomolangma area, Acta Geodaetica et Cartographica Sinica (in Chinese), 1994, 23(3): 178183.
Chen, J. Y., Chang, G., Lee, U. L. et al., Crustal movement, gravity field and atmospheric refraction in the Mt. Qomolangma, ZfV, 1994(8): 389400.
Chen, J. Y., Xui, Z., Chang, G. et al., On crustal movement in Mt. Qumolongma and its adjacent area, Acta Geophysica
Sinica (in Chinese), 1999, 39(1): 389400.
National Bureau of Surveying & Mapping, National Standard for Precise Leveling, Beijing: Publishing House of Surveying & Mapping, 1974.
Ma, Z. J., Jian, M., Strong earthquake period and strong earthquake episode in China, Chinese Earthquake (in Chinese),
1987, 3(1): 4751.
Ding, G. Y. (ed.), An Introduction to Lithospheric Dynamics of China (in Chinese), Beijing: Publishing House of Seismology, 1989.
Gu, G. H., Strain calculated by use of GPS crustal deformation in geodetic coordinates system, Crustal Deformation and
Earthquake (in Chinese), 1998, 18(3): 2024.