Building a geothermal formation model using microtremor array measurement

A comprehensive understanding of the internal structure and building a geomechanical formation model plays an important role in developing and utilizing geothermal resources. Formation models help in identifying the channel and cycling modes of the heat flow. Due to the urban sprawl and development, constructing a formation model of geothermal resources based on data from traditional geophysical methods is challenging. The Microtremor survey method was adopted to obtain critical information in Jimo, which is famous for rare seawater geothermal resources in China. Three microtremor survey lines were deployed to identify subsurface structures up to 2 km into the ground. Dispersion curves of Rayleigh waves with frequencies from 0.4 Hz to 10 Hz were extracted using the spatial auto-correlation method. An empirical equation was adopted to obtain the apparent S-wave velocity of each survey point, and plot the apparent S-wave velocity sections. The obtained sections reveal the development of two interacting faults. They form a channel for the heat-flow cycle. Two conceptual models were established to depict the formation and cycling modes of seawater geothermal resources in Jimo, based on the results and analysis. The proposed model will help verify the geothermal system and scientifically guide the development of unique geothermal resources . Moreover, the developed model verified that the microtremor survey method is effective and dependable for identifying fracture zones and strata.

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Estimation of Deep S-wave Velocity Structure in Osaka Plains Urban Area by Using Microtremor Survey Method

Journal of the Japan Society of Engineering Geology ◽

10.5110/jjseg.52.192 ◽

2011 ◽

Vol 52 (5) ◽

pp. 192-198

Author(s):

Yuichiro MINAMI ◽

Tatsurou MATSUOKA ◽

Tsuyoshi HARAGUCHI ◽

Kenta MOTOKI

Keyword(s):

Urban Area ◽

Wave Velocity ◽

Velocity Structure ◽

Survey Method ◽

S Wave ◽

Microtremor Survey

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Deep S-wave Velocity Structure in Osaka Plains Urban Area Estimated by Microtremor Survey Method

Journal of the Japan Society of Engineering Geology ◽

10.5110/jjseg.55.110 ◽

2014 ◽

Vol 55 (3) ◽

pp. 110-117 ◽

Cited By ~ 1

Author(s):

Yuichiro MINAMI ◽

Yukihiro MIZUOCHI ◽

Tatsurou MATSUOKA ◽

Tsuyoshi HARAGUCHI ◽

Kenta MOTOKI

Keyword(s):

Urban Area ◽

Wave Velocity ◽

Velocity Structure ◽

Survey Method ◽

S Wave ◽

Microtremor Survey

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Application effectiveness of the microtremor survey method in the exploration of geothermal resources

Journal of Geophysics and Engineering ◽

10.1088/1742-2140/aa7f4e ◽

2017 ◽

Vol 14 (5) ◽

pp. 1283-1289 ◽

Cited By ~ 6

Author(s):

Baoqing Tian ◽

Peifen Xu ◽

Suqun Ling ◽

Jianguo Du ◽

Xueqiu Xu ◽

...

Keyword(s):

Survey Method ◽

Geothermal Resources ◽

Microtremor Survey

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Estimation of shallow subsurface S-wave velocity structure in urban area based on inversion of apparent dispersion curve

Journal of Geophysics and Engineering ◽

10.1093/jge/gxaa054 ◽

2020 ◽

Vol 17 (6) ◽

pp. 940-955

Author(s):

Zhiwei You ◽

Peifen Xu ◽

Suqun Ling ◽

Yanan Du ◽

Ruohan Zhang ◽

...

Keyword(s):

Spatial Autocorrelation ◽

Urban Area ◽

Wave Velocity ◽

Simulated Annealing Algorithm ◽

Velocity Structure ◽

Dispersion Curves ◽

Survey Method ◽

S Wave ◽

Geological Surveys ◽

Autocorrelation Method

Abstract Due to its efficiency, convenience, non-destructive nature and strong anti-interference capability, the microtremor survey method (MSM) has found wide applications in urban geological surveys. The spatial autocorrelation method is diffusely applied to extract the dispersion curves from microtremor signals, which needs to satisfy the assumption that the energy of the fundamental Rayleigh wave is dominant. However, for layered media containing a layer with a significant low- or high-velocity contrast, this assumption is distinctly incorrect for certain frequency ranges. We present a processing methodology comprising the extraction and inversion of the apparent dispersion curves based on extended spatial autocorrelation method and fast simulated-annealing algorithm. We analyse synthetic microtremor signals for three selected geological models, and then compare the S-wave velocity structures estimated from their inversions with the actual models. Subsequently, a filed data example is given to detect the shallow stratigraphic structures in Guangzhou city, China, in which the new MSM was used. The estimated two-dimensional S-wave velocity model provided an accurate description of the thickness and depth of the strata in the study area, based on a priori information. Moreover, the S-wave velocity structures estimated from the MSM and the results from the drilling match very well, indicating that MSM is a reliable geophysical technique in urban geological surveys. Combined with available borehole information, MSM can be a very robust and effective method for detecting the shallow three-dimensional velocity structures in an urban area.

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Identifying recharge under subtle ephemeral features in flat-lying semi-arid region using a combined geophysical approach

10.5194/hess-2019-576 ◽

2020 ◽

Author(s):

Brady A. Flinchum ◽

Eddie Banks ◽

Michael Hatch ◽

Okke Batelaan ◽

Luk Peeters ◽

...

Keyword(s):

Wave Velocity ◽

Arid Region ◽

Geophysical Methods ◽

P Wave ◽

Seismic Survey ◽

Small Scale ◽

S Wave ◽

Near Surface ◽

Semi Arid Region ◽

Semi Arid

Abstract. Identifying and quantifying recharge processes linked to ephemeral surface water features is challenging due to their episodic nature. We use a unique combination of well-established near-surface geophysical methods to provide evidence of a surface and groundwater connection under a small ephemeral recharge feature in a flat, semi-arid region near Adelaide, Australia. We use a seismic survey to obtain P-wave velocity through travel-time tomography and S-wave velocity through the multichannel analysis of surface waves. The ratios between P-wave and S-wave velocities allow us to infer the position of the water table. A separate survey was used to obtain electrical conductivity measurements from time-domain electromagnetics and water contents were acquired by downhole nuclear magnetic resonance. The combined geophysical observations provide evidence to support a groundwater mound underneath a subtle ephemeral feature. Our results suggest that recharge is localized and that small-scale ephemeral features play an important role in groundwater recharge. Furthermore, we show that a combined geophysical approach can provide a unique perspective that helps shape the hydrogeological conceptualization of a semi-arid region.

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Geothermal resource potential assessment of Erdaobaihe, Changbaishan volcanic field: Constraints from geophysics

Open Geosciences ◽

10.1515/geo-2020-0282 ◽

2021 ◽

Vol 13 (1) ◽

pp. 1053-1063

Author(s):

Zhi-He Xu ◽

Zhen-Jun Sun ◽

Wei Xin ◽

Liping Zhong

Keyword(s):

Geophysical Methods ◽

Close Correlation ◽

Volcanic Field ◽

Hot Water ◽

Geothermal System ◽

Published Data ◽

Geothermal Resource ◽

Geothermal Resources ◽

Growth Zones ◽

Geothermal Drilling

Abstract Geothermal resources occurring in the Changbaishan volcanic field are directly or indirectly controlled by volcanic activity and exhibit a close correlation with deep-seated faults. Energy and thermal transfer are generally controlled by groundwater circulation and hot gas emission. This article considers the detectability of hot water and gas by geophysical methods. The controlled source acoustic magnetotelluric (CSAMT) and radon (222Rn) gas methods give straightforward information on electrical resistivity and natural radon emissions, respectively, to assess the geothermal condition. The CSAMT method detected five-banded low-apparent resistivity bodies (decreasing from 3,000 to 300 Ωm), indicating that there exists a high degree of water-bearing capacities in the subsurface. The radon (222Rn) gas concentrations were monitored in two rapid growth zones: one zone showing values ranging from 3,000 to 23,000 Bq/m3, and the other with values from 4,000 to 24,000 Bq/m3. These changes demonstrate that the heat energies available in these areas were very high and that there is potential for geothermal resources in those zones. Combining with previously published data from geothermometry and geothermal drilling, we argue that there is great potential in Erdaobaihe for geothermal exploitation and that the geothermal resource type should be classified into uplift mountain geothermal system no magma type.

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VALUATION FOR PRACTICAL USE OF S-WAVE VELOCITY STRUCTURE DETERMINED BY THE SPATIAL AUTO-CORRELATION METHOD APPLIED FOR MICROTREMORS

Journal of Structural and Construction Engineering (Transactions of AIJ) ◽

10.3130/aijs.70.17_5 ◽

2005 ◽

Vol 70 (596) ◽

pp. 17-24 ◽

Cited By ~ 1

Author(s):

Seiji TSUNO ◽

Kazuyoshi KUDO

Keyword(s):

Wave Velocity ◽

Velocity Structure ◽

Correlation Method ◽

S Wave ◽

Auto Correlation

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Cavity detection by SH-wave Full Waveform Inversion — A reflection-focused approach

Geophysics ◽

10.1190/geo2020-0349.1 ◽

2021 ◽

pp. 1-65

Author(s):

Rebekka Mecking ◽

Daniel Köhn ◽

Matthias Meinecke ◽

Wolfgang Rabbel

Keyword(s):

Wave Velocity ◽

Automatic Gain Control ◽

Waveform Inversion ◽

Geophysical Methods ◽

Gain Control ◽

Full Waveform Inversion ◽

S Wave ◽

Low Velocity ◽

Full Waveform ◽

Tunnel System

The detection of cavities with geophysical methods is a challenging task for which a general approach has not yet been found. We show that viscoelastic SH full waveform inversion (FWI), focusing primarily on reflection events, is able to accurately locate the position of cavities, areas of decompacted sediments and, more generally, seismic low-velocity anomalies down to 30 m depth. The key for a successful FWI application is the enhancement of the reflected wavefield relative to the surface wavefield. For this purpose, we applied automatic gain control normalization in the objective function. By focusing the inversion on the reflected wavefield, we demonstrate that one can differentiate between air-filled cavities with zero shear-wave velocity and low-velocity zones. Additionally, we test the FWI approach on a field dataset, with a known collapsed tunnel system inside a 32 m high, monumental, antique grave mound. The results show that the location and extent, as well as density and S-wave velocity of the collapsed tunnel system, can be determined with sufficient accuracy by applying a 2D FWI approach to intersecting profiles, despite the 3D nature of the problem.

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