Seismic Refraction Exploration for Groundwater Potential Evaluations: A Case Study of Vientiane Province, Laos

VNU Journal of Science: Earth and Environmental Sciences, Vol. 36, No. 4 (2020) 90-101 
90 
Original Article 
Seismic Refraction Exploration for Groundwater Potential 
Evaluations: A Case Study of Vientiane Province, Laos 
Viengthong Xayavong1,3, , Vu Duc Minh1, Nguyen Anh Duong2, 
Vu Minh Tuan2 
1VNU University of Science, 334 Nguyen Trai, Hanoi, Vietnam. 
2Institute of Geophysics, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam. 
3Faculty of Natural Science, National University of Laos, Dongdok Campus 7322, Vientiane, Laos. 
Received 25 June 2020 
Revised 24 August 2020; Accepted 31 August 2020 
Abstract: Recently, there has been increased interest in the use of seismic refraction surveys for the 
exploration of groundwater investigations. The aim of this study is to delineate groundwater 
potential zones using the seismic refraction technique. SmartSeis ST, with 12 channels seismograph 
was selected for seismic refraction data acquisition in Phonhong district of Vientiane Province, Laos. 
The seismic velocities distribution analysis indicated that there are three different subsurface 
lithological zones ranging between (300–750m/s), (700–1650m/s), and (1500–2100m/s). Gradual 
increase of seismic velocity indicates changes of lithological layers with vertical depth. This velocity 
increase is due to the dense lithological formation which changes vertically deep from alluvial 
sediments to dry sand and then to siltstone and gravel layers according to the borehole data. The 
seismic refraction results show that the aquifer is a sand and gravel aquifer with a thickness of 
unclear. The depth to the groundwater saturated layers ranging from 10 m to 25 m. The results of 
this study have indicated that the application of the seismic refraction exploration method to find 
groundwater is feasible and effective and can delineate groundwater potential zones in Laos. 
Keywords: Groundwater, aquifers, seismic refraction exploration, Vientiane, Laos. 
________ 
 Corresponding author. 
 E-mail address: viengthongxv@gmail.com 
 https://doi.org/10.25073/2588-1094/vnuees.4651 
V.T. Xayavong et al. / VNU Journal of Science: Earth and Environmental Sciences, Vol. 36, No. 4 (2020) 90-101 91 
1. Introduction 
Groundwater is an essential source as 
freshwater in around the world, whereas a 
growing number of countries in Southeast Asia 
have encountered serious groundwater quantity 
and quality problems such as declining 
groundwater tables, subsidence, groundwater 
quality, and overexploitation leading to 
unsustainable management of groundwater 
resources. These are major problems currently 
challenging hydrogeologists and relevant 
organizations. Properly managed, groundwater 
is a renewable resource, with volume varying 
with the seasons and character of the local 
geology. Available volumes of surface water 
may vary very strongly over time, and surface 
water may be susceptible to various forms of 
pollution. Groundwater is an important source 
for irrigation, industries, and for both drinking 
and domestic purposes, but the mindless pursuit 
for utilizing more groundwater by all the users 
has already started conducting tremendous 
pressure on this essential resource [1]. 
The potash reserves in the Thangon area of 
the Vientiane basin are considerable, with an 
estimated 50.3 billion tonnes of ore grading 15% 
potassium chloride [2]. Gypsum is mined e.g. at 
the Ban Iaomakkha mine in the Savannkhet area 
to the south, where reserves are estimated to be 
at least 50 million tonnes. While minerals are 
significant, the Lao economy is dominated by 
agriculture, which represents most of the 
employment in the country and about half of the 
GDP. Together with the climatic conditions, this 
means that effective management of water 
resources is vital for sustained and effective 
economic growth. As the economy has grown, 
loads on water resources have increased, 
requiring more advanced approaches to long-
term management. 
In Laos, information and programs for the 
monitoring and evaluation of groundwater 
quantity and quality are limited. For example, a 
drilling project in the 1990s in Vientiane 
Province was implemented by Japan 
International Cooperation Agency (JICA) for 
domestic supply in rural areas [3]. 
Unfortunately, 60% of the 118 deep wells drilled 
were could not be used due to poor water quality, 
such as high salinity [4]. As drilling is expensive, 
it will be of great benefit if advanced geophysical 
methods, especially seismic refraction 
exploration applied as reliable tools for 
groundwater investigation and management [5]. 
Nils et al. (2011a) conducted research on 
characterization of aquifers in the Vientiane 
Basin, Laos, using Magnetic Resonance 
Sounding and Vertical Electrical Sounding [20]. 
Both MRS and VES were carried out at three 
areas namely Xaythani (Thangon), Thoulakhom 
and Phonhong districts of Vientiane Basin. 
The porous aquifers are described indirectly 
through the relationship between the lithological 
features and the body wave velocity. Several 
approaches have been suggested that the 
groundwater level is attributed to specific VP 
values [6-9] or the hypothetic aquifer layer is 
determined via its VP/VS ratio [10-12] or 
Poisson's ratio [13]. Besides, the more complex 
theoretical approaches which are based on the 
principles of the elastic wave propagation within 
saturated and unsaturated porous media have 
been proposed [14]. These approaches require a 
comprehensive knowledge of the lithological 
sequences of the investigating site. Meanwhile, 
Grelle and Guadagno (2009) conducted research 
entitle seismic refraction methodology for 
groundwater level determination at three 
different research sites at Campania region in 
Italy with the known geological sequences 
information [15]. 
In this study, we use the seismi ... layers found blue colours 
and seismic velocity range from 1500 to 2000 
m/s with an average of 1750m/s, corresponds to 
an area which is mainly gravel and siltstone with 
the depth from ground surface to the third layer 
is greater than 15m indicating suitable areas for 
groundwater potential zones. It is clearly when 
we compare the velocity with that of water or 
sand (saturated) materials in Table 2. 
Meanwhile, two parallel north-south 
transverse seismic profiles namely profile 3 and 
4 at site 2 showed similar results. The traveltime 
curves and velocity models are shown in (Fig. 8 
and 9). The P-wave velocity of topmost layers, 
where lowest seismic velocities ranging from 
300 to 750m/s with an average velocity of 
525m/s were detected, corresponds to an area 
within the sand and clay top soil which is mainly 
as dry alluvial sediments, whereas the thickness 
of the first layers range from 5 to 10m. The 
second layers made up of the yellowish green 
colours and seismic velocity ranges from 750 to 
1650 m/s with an average of 1200m/s were 
detected, corresponds to an area which is mainly 
thick saturated clayey layer and the thickness of 
the second layer ranges between 10 to 20m. The 
third layers made up blue colours and seismic 
velocity range from 1650 to 2100 m/s with an 
average of 1875 m/s were detected, corresponds 
to an area which is mainly gravel and siltstone 
with the depth from ground surface to the third 
layer is greater than 20m indicating suitable 
areas for groundwater potential zones.
V.T. Xayavong et al. / VNU Journal of Science: Earth and Environmental Sciences, Vol. 36, No. 4 (2020) 90-101 97 
Figure 6. The traveltime curves and velocity models for seismic profile 1 at site 1. 
Figure 7. The traveltime curves and velocity models for seismic profile2 at site 1. 
The results of seismic refraction technique 
found the depth of the main aquifer ranges from 
18 to 20 m that respond well with Magnetic 
Resonance Sounding and Vertical Electrical 
Sounding at three areas namely Xaythani 
(Thangon), Thoulakhom and Phonhong districts 
of Vientiane Basin [27]. The results from the 
MRS measurements show that the aquifer 
thickness ranges from 10 to 40 m and the depth 
of the main aquifer ranges from 5 to 15 m [27]. 
The free water content is up to 30% and the 
decay times vary between 100 and 400 ms, 
suggesting a mean pore size equivalent to fine 
sand to gravel while the resistivity of the aquifers 
is highly variable but is usually higher than 10 
Ω-m suggesting that the water is fresh [27]. 
Meanwhile, determining water quality 
parameters of aquifers in the Vientiane basin, 
Laos used geophysical and water chemistry data 
[28]. The results found water layers are 
identified with the main water layer situated 
between 13–30 m in depth with no water below 
[28]. From the VES models it becomes clear that 
the low-resistive layer (3 Ωm) starts between 
34–37 m, which is an indication that this layer is 
most likely clay (Fig.11) [21]. In additionally, 
drilling found the water table at a depth of 20 m 
in Phonhong district. Soil samples collected 
from this depth have been identified as gravel 
and siltstone, matching the velocity model result. 
The detailed soil profile is included in Fig. 10b. 
The different geological formations observed 
from the borehole 1 (BH 1) stratigraphy data 
matched well with the seismic results (Table 3). 
Integrated seismic and drilling results at 
seismic profile 1 where is Naxou village, which 
correlated well with vertical electrical sounding 
at site S19 of Nils et al. (2011a) (Fig.3), indicated 
that found water table range from 15 to 30m with 
average seismic velocity around 1875m/s is 
considered as gravel and siltstone aquifers in 
research sites. According to the seismic 
exploration results, the thickness of all three 
layers of Site 2 at Phonhor village is larger than 
that of Site 1 at Naxou village. It means that the 
aquifer layer (N2Q1) at Site 2 is thicker than that 
at Site 1.
V.T. Xayavong et al. / VNU Journal of Science: Earth and Environmental Sciences, Vol. 36, No. 4 (2020) 90-101 98 
Figure 8. The traveltime curves and velocity models for seismic profile 3 at site 2. 
Figure 9. The traveltime curves and velocity models for seismic profile 4 at site 2. 
Table 3. Comparison between drilling results at BH 1 and seismic result of velocity model 
Drilling results at BH 1 Velocity model results at profile 1 
Depth (m) Stratigraphy Depth (m) Velocity range (m/s) Stratigraphy 
0-5 Clay and sand top soil 
0-10 300-750 Clay and sand top soil 5-8 Sandy and clay 
8-12 Clay and sand 
12-15 Mudstone and clay 
10-20 750-1650 
Sandy clay 
15-20 Sand 
20-22 
Gravel and siltstone 
(water table) 
22-25 Siltstone >20 1650-2100 
Gravel and siltstone 
(water table, aquifers) 
V.T. Xayavong et al. / VNU Journal of Science: Earth and Environmental Sciences, Vol. 36, No. 4 (2020) 90-101 99 
Figure 10. (a) Seismic velocity model under profile 1 at site1 and (b) vertical geological section 
of borehole 1 (BH 1) at 440 m along profile 1. 
5. Conclusion 
The seismic refraction exploration method 
has proved useful in subsurface mapping in earth 
layers depends on depth. In Phonhong district, 
the average seismic velocities of 600 m/s for the 
upper layer, interpreted as alluvium sediments 
with thickness of 5 m. The middle layer has a 
thickness of 14 m and average seismic velocities 
of 1200 m/s and is interpreted as thick saturated 
clayey layer. Third layer's average velocities are 
1750 m/s and are interpreted as gravel and 
siltstone (water saturated) with 18m vertical 
extensions. This result is agreement with the 
drilling results of borehole 1 at site 1 in the 
Phonhong district found the water table at depth 
20 m and the soil sample collected at this depth 
has been identified as gravel and siltstone. 
According to velocity and lithology of third 
layer, which could form good reservoir for 
groundwater potential, were identified. The 
change in velocity may largely be as a result of 
the variation in subsurface lithology, texture, 
structure, grain size, compaction, cementation 
and the level of groundwater saturation. 
Thickness of all three layers has gradually 
increasing from northern to southern part of the 
study site 2. The results of this research work 
have indicated that the application of the seismic 
refraction exploration method to find 
groundwater in Laos is feasible and effective and 
can delineate groundwater potential zones in the 
study areas. 
Acknowledgements 
The authors are grateful to the International 
Science Programme (ISP) of Uppsala 
University, Sweden for funding the research 
work. The authors would like to express our 
deepest appreciation to Department of Physics, 
Faculty Natural Science, National University of 
Laos for supporting the SmartSeis ST (USA) and 
Department of Geology and Mines of Laos for 
geological information in the study areas. 
References 
[1] H. Kyoochul, T.M.N. Nguyen, L. Eunhee, J. 
Ramasamy, Current Status and Issues of 
Groundwater in the Mekong River Basin, Korea 
Institute of Geoscience and Mineral Resources 
(KIGAM) (2017) 1-125. https://bangkok.unesco. 
org/content/current-status-and-issues-groundwater 
-mekong-river-basin (accessed 16 April 2020). 
V.T. Xayavong et al. / VNU Journal of Science: Earth and Environmental Sciences, Vol. 36, No. 4 (2020) 90-101 100 
[2] M. Masaharu, Final Report for Economic Geology, 
the World Bank Washington DC (2006). 
[3] Japan International Cooperation Agency (JICA). 
The study on rural water supply and sanitation 
improvement in the northwest region in the Lao 
People's Democratic Republic, Ministry of health, 
National centre for environmental health and water 
supply, Progress report 2 (2000) 14. 
[4] K. Takayanagi, Basic Design Study Report on the 
Project for Groundwater Development in Vientiane 
Province in Laos PDR, Japan International 
Cooperation Agency (JICA) (1993). 
[5] C. Chiemeke, and Aboh, Delineation of aquiferous 
layers within the basement complex using joint 
inversion of seismic refraction tomography and 
high resolution 3D seismic reflection survey, Arch. 
Applied Sci. Res 4 (2012) 400-405. https://www. 
researchgate.net/publication/282768427_Delineati
on_of_aquiferous_layers_within_the_basement_c
omplex_using_joint_inversion_of_seismic_refract
ion_tomography_and_high_resolution_3D_seismi
c_reflection_survey (accessed 16 April 2020). 
[6] A.A.R Zohdy, G.P. Eaton, D.R. Mabey,1974. 
Application of surface geophysics to groundwater 
investigation. U.S. Geol. Surv. Techniques of Water -
Resource Investi- gations, book 2, chapter D1. 
[7] J.E. Sander, The blind zone in seismic ground-
water exploration, Ground Water 165 (1978) 394-
395. https://doi.org/10.1111/j.1745-6584.1978.tb0 
3252.x 
[8] F.P. Haeni, Application of seismic refraction 
methods in groundwater modelling studies in New 
England. Geophysics 51 (2) (1986) 236-249. http:// 
dx.doi.org/10.1190/1.1442083. 
[9] B. Hasselstroem, Water prospecting and rock-
investigation by the seismic refraction method. 
Geoexploration 7 (2) (1969) 213. https://doi.org/ 
10.1016/0016-7142(69)90026-X. 
[10] H. Stümpel, S. Kähler, R. Meissner, B. Milkereit, 
The use of seismic shear waves and compressional 
waves for lithological problems of shallow 
sediments. Geophysical Prospecting 32 (1984) 
662-675. https://doi.org/10.1111/j.1365-2478. 
1984.tb01712.x. 
[11] J.P. Castagna, M.L. Batzle, R.L. Eastwood, 
Relationship between compressional-wave and 
shear-wave velocities in clastic silicate rocks. 
Geophysics 50 (4) (1985) 571-581. https://doi.org/ 
10.1190/1.1894108. 
[12] C. Nicholson, D.W. Simposon, Changes in VP/VS 
with depth: implication for appropriate velocity 
models, improved earthquake locations, and 
material proper- ties of the upper crust. Bulletin of 
the Seismological Society of America 75 (1985) 
1105-1124. https://pubs.geoscienceworld.org/ssa/ 
bssa/article-abstract/75/4/1105/118773/Changes-
in-Vp-Vs-with-depth-Implications-for?redirected 
From=fulltext (accessed 16 April 2020). 
[13] J.M. Lees, H. Wu, Poisson's ratio and porosity at 
Coso geothermal area, California. Journal of 
volcanology and geothermal research 95 (2000) 
157-173. https://doi.org/10.1016/S0377-0273(99) 
00126-2. 
[14] S. Foti, C.G. Lai, R. Lancellotta, Porosity of fluid-
saturated porous media from measured seismic 
wave velocities. Geotechnique 52 (5) (2002), 359-
373.  
[15] G. Grelle, F.M. Guadagno, Seismic refraction 
methodology for groundwater level determination: 
“Water seismic index”. Journal of Applied 
Geophysics 68 (2009) 301-320. https://doi.org/10. 
1016/j.jappgeo.2009.02.001. 
[16] M. El Tabakh, C. Utha-Aroon, B.C. Schreiber, 
Sedimentology of the Cretaceous Maha Sarakham 
evaporites in the Khorat Plateau of northeastern 
Thailand, Sedimentary Geology 123 (1999) 31-62. 
https://doi.org/10.1016/S0037-0738(98)00083-9. 
[17] R.J. Hite, W. Japakasert, Potash deposits of the 
Khorat Plateau, Thailand and Laos, Economic 
Geology 74 (1979) 448-458.  
2113/gsecongeo.74.2.448. 
[18] S. Keith, P. Crosby, Overview of the Geology and 
Resources of the APPC Udon Potash (Sylvinite) 
Deposits, Udon Thani Province, Thailand. 
International Conference on Geology, 
Geotechnology and Mineral Resources of 
Indochina (GEOINDO 2005), Khon Kaen, 
Thailand (2005) 283-299.  
go.id/index.php/9-mineral-article-1/mineral-
article/130-overview-of-the-geology-and-
resources-of-the-appc-udon-potash-sylvinite-
deposits-udon-thani (accessed 16 April 2020). 
[19] F.L.S. Paul, B.S. Robert, B. Charlie, C. Andrew, 
Mid-Cretaceous inversion in the Northern Khorat 
Plateau of Lao PDR and Thailand, Tectonic 
Evolution of Southeast Asia, 106 (2016), 233-247. 
[20] Z. Xiying, M. Haizhou, M. Yunqi, T. Qiliang, Y. 
Xiaolong, Origin of the late Cretaceous potash-
bearing evaporites in the Vientiane Basin of Laos, 
Journal of Asian Earth Sciences 62 (2013) 812-
818. https://doi.org/10.1016/j.jseaes.2012.11.036. 
[21] K. Phommakaysone, Urban geology of Vientiane 
municipality, capital of the Lao people’s 
Democratic Republic, Atlas of Urban Geology 14 
(2001) 341-346. 
[22] M. Raksaskulwong, D. Monjai, Relationship 
between the Maha Sarakham Formation and high 
V.T. Xayavong et al. / VNU Journal of Science: Earth and Environmental Sciences, Vol. 36, No. 4 (2020) 90-101 101 
terrace gravels along the Khon Kean-Kalasin 
provinces. (Geothai’07), Department of Mineral 
Resources, Bangkok, Thailand (2007) 288-296. 
Yearbooks/M_1/2007/12735.pdf (accessed 16 
April 2020). 
[23] N.X. Long, N.X. Lam, N.D. Canh, Report on 
Geological data for Potassium and Manganese in 
Thangon. Department of Geology and Mining, 
Vientiane, Laos (1986). 
[24] P. Kearey, M. Brooks, I. Healy, An Introduction to 
Geophysical Exploration. 3rd ed. Blackwell 
Science (2002). 
[25] M. Stuart-Fox, D.F. Rooney. Microsoft Encarta, 
(2006). 
[26] S.A. Adedibu, C.O. Abimbola. Insight into seismic 
refraction and electrical resistivity tomography 
techniques in subsurface investigations, The 
Mining-Geology-Petroleum Engineering Bulletin 
(2019) 93-111.  
2019.1.9. 
[27] P. Nils, W. Kamhaeng, P. Khamphouth, E. Sten-
Ake, Characterization of aquifers in the Vientiane 
Basin, Laos, using Magnetic Resonance Sounding 
and Vertical Electrical Sounding. Journal of 
Applied Geophysics 73 (2011a) 207-220. https:// 
doi.org/10.1016/j.jappgeo.2011.01.003. 
[28] P. Nils, W. Kamhaeng, P. Khamphouth, E. Sten-
Ake, Determining water quality parameters of 
aquifers in the Vientiane Basin, Laos, using 
geophysical and water chemistry data, Near 
Surface Geophysics 9 (2011b) 381-395. https://doi. 
org/10.3997/1873-0604.2011014.