Utilization of seismic refraction data for the study of structure of Bang hot-water source, Le Thuy, Quang Binh

Abstract

Study of  the geological structural elements in the area of geothermal sources is important for identifying the geothermal reservoir, the object is capable of energy production. This paper presents the preliminary results of the structural study obtained by the seismic refraction data in the area of hot water spring Bang, Le Thuy, Quang Binh. The exploration was carried out in 2014 by using 150 wireless Texan instruments produced by Refraction Technology Company - USA and provided by the Institute of Earth Sciences, Academia Sinica, Taiwan. The data were collected from 4 profiles,  cutting several tectonic faults  around the exposed hot water source. The seismic signals were strong on the records of each instrument, especially the signals of refraction wave. The 2D seismic tomographic technique is applied for data interpretation to create the velocity structural models from 4 observation profiles. Based on the velocity structures, the area can be separated into three main structural layers, characterized generally by three velocity ranges: 3,0 – 4,1 km/s; 4,2 – 5,1 km/s and 5,2 – 6,1 km/s, respectively.

The block separation by the faults of different size with the subsidence tendency from southwest to the northeast parts of the  region is apparently reflected in the seismic  data obtained in this study.  The narrow lower velocity vertical structure detected inside the southern well-consolidated rock uplifted block away  from the exposed hot water source more than 2 km, under the  sub meridian extension Quaternary structure probably related to the breaking up of the bedrocks caused by the tectonic activity in the region. Perhaps, the object played a role as the thermal fluid channel in the  geological history time and  is closely related to the geothermal reservoir predicted recently by magnetotelluric investigations  in this  location.

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