Borehole Drilling Research Articles

Granite Exploration by using Electrical Resistivity Imaging (ERI): A Case Study in Johor

Electrical Resistivity Imaging (ERI) is a tool used in near surface geophysical surveys by flowing an electric current through electrodes that were injected into the ground. The usage of electrical resistivity imaging (ERI) method dominated by geophysicist has increased tremendously in geotechnical engineering application owing to the efficiency and effectiveness of the method in term of time, cost and also data coverage. The survey performed with respect to the particular reference to ERI in determining the granite rock underneath the ground. There were seven (7) lines of ERI performed at the study area by using ABEM Terrameter LS 2 set of equipment based on Schlumberger protocol. Six (6) boreholes were also drilled to obtain engineering properties of rock at the study area. In order to develop the relationship between resistivity and engineering properties, a comparison between borehole field test result and the resistivity value were made. Results from the ERI indicated the presence of zones with high resistivity values identified as overburden soil, fractured granite and solid granite. The findings of this study also showed that the electrical resistivity imaging coupled with borehole drillings were applicable tools for the determination of the granite rock underneath the ground via subsurface profiles and such as depth of overburden soil and engineering properties of soil. In conclusion, ERI is a method that does not disturb the structure or the function of the soil which successfully became the best method in exploring the granite rock.

Integrated Geophysical and Packer Test for the Water Tightness Evaluation of Gullele Botanic Garden Dam Site, Northwest of Addis Ababa, Ethiopia

Gullele Botanic Garden is one of the largest botanical gardens in Ethiopia, which is found northwest of Addis Ababa. For this garden, a dam was proposed to be constructed for irrigation and recreational purposes. The intended dam will have a height of 30 m and a dam axis length of around 180 m. The main objective of this work is to investigate and evaluate the engineering geological aspects of the proposed dam site based on detailed geological, geotechnical and geophysical investigations. The investigation conducted in the area includes, electrical resistivity imaging, VES, borehole drilling and single packer permeability test. Geologically the area is covered by the different volcanic rock such as ignimbrite, rhyolite, tuff, basalt, and residual soil; and geological structures such as joint, fracture, flow banding, and cooling joint. The dominant orientations of geological structures are N-S and E-W directions. Results from different investigations revealed that three geotechnical layers were identified. These are overburden (completely weathered ignimbrite and soil), highly to moderately weathered ignimbrite and moderately to slightly weathered ignimbrite rock mass. The rock mass permeability test from six boreholes has Lugeon values ranging from 0 to 9. The maximum Lugeon (permeability of the rock mass) values investigated at the left abutment and riverbed of the proposed dam site showed wash out and dilation behavior respectively. The permeability result indicates that possible seepage problem at left abutment, riverbed and reserviour of the proposed dam. Therefore, during the construction of the dam, those specific locations, which are identified as problematic areas, need effective ground improvement works and special monitoring.

An empirical relationship between resonance frequency, bedrock depth and VS30 for Croatia based on HVSR forward modelling

Seismic bedrock depth represents one of the crucial steps in site response analysis as the input seismic ground motion is propagated from the bedrock level through soil profile column to estimate surface ground motion. In the last two decades, several studies estimated bedrock depth using microtremor horizontal-to-vertical-spectral ratio fundamental (resonance) frequency and known (mostly boreholes) bedrock depth in different regions through power-law regression. In this study, seismic bedrock (H800—depth of the bedrock formation identified by shear wave velocity VS ≥ 800 m/s) is estimated using H/V forward modelling routine in which shear wave velocity profile from geophysical measurements was used as an initial soil model. Based on geological, geophysical and microtremor data, empirical relationships between average shear wave velocity in top 30 m, resonance frequency and bedrock depth are derived. Given evaluation of sedimentary thicknesses showed to be within the range of published studies for similar geological and site characteristics if the errors between different methods, approaches and site parameters are considered. The main limitation to validate proposed relationships is the lack of realistic deep borehole data like in similar studies. Further work is required that should include deep data from borehole drilling, seismic refraction and reflection or vertical electrical sounding. The intention is that presented regressions between resonance frequency, bedrock depth and VS30 would be implemented into nonlinear site amplification model and further development towards Ground Motion Prediction Equations for Croatia.

Manual Borehole Drilling as a Cost-Effective Solution for Drinking Water Access in Low-Income Contexts

Water access remains a challenge in rural areas of low-income countries. Manual drilling technologies have the potential to enhance water access by providing a low cost drinking water alternative for communities in low and middle income countries. This paper provides an overview of the main successes and challenges experienced by manual boreholes in the last two decades. A review of the existing methods is provided, discussing their advantages and disadvantages and comparing their potential against alternatives such as excavated wells and mechanized boreholes. Manual boreholes are found to be a competitive solution in relatively soft rocks, such as unconsolidated sediments and weathered materials, as well as and in hydrogeological settings characterized by moderately shallow water tables. Ensuring professional workmanship, the development of regulatory frameworks, protection against groundwater pollution and standards for quality assurance rank among the main challenges for the future.

Efficacy of Geophysical Techniques for Groundwater Exploration in the Volta Basin, Northern Region of Ghana

Abstract
 Groundwater, traditionally extracted from hand-dug wells and boreholes is the main drinking water source in the Northern Region of Ghana. Many boreholes have been constructed in the region to increase accessibility to potable water mainly as part of rural water supply projects where borehole siting has to be relatively cheaper. These projects have resulted in low success rates of borehole drilling because of the application of inefficient and simple geophysical techniques supposed to be cheaper. Field surveys were conducted with the Electrical Resistivity Imaging (ERI) technique, Electrokinetic System (EKS) sounding technique and Radon (222Rn) technique with the objectives of determining the best geophysical methods for borehole siting and its efficiency in the Volta Basin (VB) in the Northern Region of Ghana. The surveys were conducted at stations of existing dry and positive boreholes. Results show that the three geophysical techniques are efficient to identify groundwater accumulation zones. The ERI, EKS and 222Rn are efficient to identify discontinuities, calculate hydraulic conductivity of discontinuities and identify areas of water circulation respectively. It is recommended that the ERI be used to obtain discontinuities and weak zones for drilling on rural water supply projects in the VB. The EKS and 222Rn should be conducted to evaluate these features when high yield boreholes are required.
 
 Keywords: Geophysical Techniques, Volta Basin, Borehole Drilling, Success Rates

Multidisciplinary Study of Subsidence and Sinkhole Occurrences in the Acque Albule Basin (Roma, Italy)

AbstractWe present the results of a combined analysis of remote sensing and geophysical‐geotechnical data carried out in the Acque Albule Basin, a sinkhole prone area located close to the city of Roma, where a wide travertine wedge is present. We carried out geophysical measurements and borehole drillings over two test areas to image the subsoil where paroxysmal surficial dynamics occur. One site is marked by subsidence occurring at least since the early 2000s, whereas the other site hosts the “La Regina” and “Colonnelle” sinkhole lakes, which discharge sulfur‐carbonated waters. The stability of these two sites threatens highway, railway, and airport facilities, and this study helps to assess the geological hazard. For example, InSAR and LiDAR data helped define wide scale subsidence over the last 20 years and previously undetected small‐scale morphologies. Geophysical measurements of the latter revealed shallow and deep dissolution affecting the travertine and driving surficial paroxysmal events. Both study sites were found to lie inside a large depression located at the junction between Jurassic carbonate and Plio‐Pleistocene units in association with paleo karst morphologies in the travertine deposits and affected by the present‐past spillage of sulfurous waters. Given these elements, multidisciplinary geophysical observations are crucial for assessing and mitigating the geological risk and guiding land use planning and management.

Engineering geological assessment and determination of bearing capacity of the Buyukyenice dam site (Balıkesir, Turkey)

Rock mass evaluation for the foundations of the Buyukyenice impervious central core rockfill dam to be constructed in the southwestern part of Balikesir, Turkey, was investigated. The geology under the foundation of the dam site is composed of silty clayey sandstone, silty sandstone, sandstone, tuff, and agglomerate tuff. The study involves three stages of field and laboratory studies and determination of bearing capacity of the foundation on which the dam body will be constructed. Detailed discontinuity surveys, geotechnical borehole drilling, Lugeon permeability tests, and sampling for index and some mechanical tests were performed in the field. Unit weight, apparent porosity, water absorption by weight, uniaxial compressive strength, and tensile strength tests were carried out on collected samples. The engineering classification of the rock masses at the dam site was evaluated by considering rock mass rating (RMR), rock mass quality (Q), rock mass index (RMi), and geological strength index (GSI). As a general conclusion, the rock mass at the dam site was divided into three classes from fair to very poor rock. Finally, the bearing capacity of the dam foundation rocks was computed for safe design.

Ocean mixing and heat transport processes observed under the Ross Ice Shelf control its basal melting

The stability of large Antarctic ice shelves has important implications for global sea level, sea ice area, and ocean circulation. A significant proportion of ice mass loss from these ice shelves is through ocean-driven melting which is controlled by largely unobserved oceanic thermodynamic and circulatory processes in the cavity beneath the ice shelf. Here we use direct measurements to provide evidence of the changing water column structure in the cavity beneath the Ross Ice Shelf, the planet's largest ice shelf by area. The cavity water column data exhibit both basal and benthic boundary layers, along with evidence of tidally modulated and diffusively convecting internal mixing processes. A region of thermohaline interleaving in the upper-middle water column indicates elevated diffusion and the potential to modify the cavity circulation. The measurements were recorded using the Aotearoa New Zealand Ross Ice Shelf Program hot water drill borehole melted in the central region of the shelf in December 2017 (HWD2), only the second borehole through the central region of the ice shelf, following J9 in 1977. These data, and comparison with the 1977 data, provide valuable insight into ice shelf cavity circulation and aid understanding of the evolution of the presently stable Ross Ice Shelf.

Bioavailability of heavy metal load in soil, groundwater, and food crops manihot esculenta and carica papaya in dumpsite environment

The need for consciousness of the impact of heavy metal on crop production and human health risk through policy formulation necessitated the study. Screening of the total heavy metal iron (Fe), nickel (Ni), cadmium (Cd), lead (Pb), chromium (Cr), and copper (Cu) concentration in soils collected at random at a depth of 0–30 cm within and around dumpsite environment in Ikhueniro, Iguomo, and Okhuahe suburban communities, Benin City, Nigeria was carried out. Cassava tubers, Pawpaw pods (manihot esculenta and carica papaya) cultivated and groundwater within and around the dumpsite environment were also tested for the selected heavy metal. The study employed integrated scientific methods in actualizing its aim. The results show that mean values of 520.97 ± 1.66 mg/kg Fe, 39.07 ± 0.33 mg/kg Ni, 1.41 ± 0.10 mg/kg Cd, 1.92 ± 0.00 mg/kg Pb, 1.24 ± 0.02 mg/kg Cr, and 24.97 ± 5.16 mg/kg Cu were recorded for soil. On the other hand, 127.00 ± 2.01: 22.36 ± 1.20 mg/kg Fe and 5.70 ± 2.11: 0.98 ± 1.11 mg/kg, respectively, amongst other metals measured in cassava and pawpaw. The results were compared to Standard Organization of Nigeria (SON), National Food and Drug Administration Control (NAFDAC), and Food and Agricultural Organisation/World Health Organisation (FAO/WHO) standards; it was observed that Fe, Ni, and Pb exceeded the threshold values for metal concentration in soil and drinking water. Policy formulation restricting farming and drilling of boreholes within the locus of dumpsite environment is advocated to fostering the attainment of green environment for sustainable development and public consciousness of the detrimental effects of heavy metals on human health.

Investigation of Geological Anomalies at Pile Foundation Location in Urban Karst Areas Using Single Borehole Radar

Karst geological anomalies at pile locations significantly affect the bearing capacity and construction safety of the piles, posing a significant challenge for urbanization. Borehole geophysical methods are required to extend the detection range and identify karst voids that are at pole locations and near drilled boreholes. In this paper, we developed a near offset and small diameter single borehole ground penetration radar (GPR) prototype. A signal processing method combining complex signal analysis by Hilbert transform (HT) and medium filtering was suggested to differentiate the weak backscattered wave from borehole background noise. A controlled horizontal borehole experiment was used to demonstrate the applicability of the prototype and the advantages of the signal analysis method prior to application in a real project. The controlled test presented three typical wave events corresponding to a soil–rock interface, rock fractures, and karst voids. Field tests were conducted at a freeway bridge extension project in an urban karst area. Multiple karst voids, sinkholes, rock fractures, and integrated bedrock were identified by analysis of four typical detection scenarios. The remediation of the karst voids and a rotary bored piling with real-time steel casing construction strategy were designed based on the investigation results. The construction feedback demonstrates that single borehole radar detection is effective for the investigation of anomalies at pile locations in urban karst areas.

New <i>Chikyu</i> Shallow Core Program (SCORE): exploring mass transport deposits and the subseafloor biosphere off Cape Erimo, northern Japan

Abstract. The Chikyu Shallow Core Program (SCORE) has been started to provide more opportunities for the scientific ocean drilling of shallow boreholes (up to 100 m) during a short-term expedition. The proposal flow is a simplified version of that of the International Ocean Discovery Program (IODP). Although there are several limitations for a SCORE project, the opportunity to retrieve 100 m of continuous core samples will be of great interest for the scientific ocean drilling community in multiple disciplines. The first expedition of the SCORE program was implemented off Cape Erimo, Hokkaido, northern Japan. The target of the drilling was to investigate the impact of submarine mass transport on the subseafloor sedimentary biosphere. In the preliminary observation of the core samples, including X-ray computed tomography (CT) scan image analysis, chaotic and inclined beds were found and interpreted as mass transport deposit (MTD) units.

Application of magnetotelluric geophysical technique in delineation of zones of high groundwater potential for borehole drilling in five communities in the Agona East District, Ghana

Hydrogeological investigations to delineate zones of high groundwater potential in five selected communities in the Agona East District of Ghana have been successfully carried out using the magnetotelluric geophysical technique. The technique has successfully been applied to delineate potential zones of high groundwater potential in terms of location and depth-to-aquifer zones. The study has revealed that the apparent electrical resistivity of the subsurface of the study area to a depth of 300 m displays the stratigraphic layers of different resistivities. Eburnean Plutonic suite and the Tamnean Plutonic Suite were the two major geologic materials encountered in the study area. The Eburnean Plutonic suite shows relatively low resistivity rang of 0–480 Ωm at a depth of 0–300 m which indicates the presence of weathered zones capable of holding water. However, the Tamnean Plutonic Suites shows a resistivity range of 200–2800 Ωm which shows that it is a consolidated rock with no developed primary and/or secondary hydrogeological properties such as porosity and permeability. Therefore, the exploration of groundwater in the Tamnean Plutonic Suite depends strictly on the fracture zones which may contain water. Again, the study revealed that the prevailing aquifer systems of the study area are not regional but are controlled by fractures and weathered zones. Therefore, it is highly envisaged that groundwater would be intersected at the saprock region which is the fractured and weathered zone between fresh bedrock and the regolith at the depth of 80–100 m. Also, the study has shown the capability of the magnetotelluric geophysical technique to delineate zones of high groundwater potentials for borehole drilling purpose.

Rock burst criteria and control based on an abutment‐stress‐transfer model in deep coal roadways

AbstractWith the increase in cover depth of the coal seam, more and more rock bursts have occurred in deep coal roadways. The conventionally used passive preventive measures are not sufficient to reduce rock burst hazards in deep coal mines. To address this problem, this study firstly evaluated the abutment stress applied to the roadway surrounding rock by constructing an abutment‐stress‐transfer model after roadway excavation. Then, according to different positions of roadways in the coal seam, roadways are classified into three types: shallow‐buried roadway with hard surrounding coal/rock; deep‐buried roadway with soft surrounding coal/rock; and medium‐deep–buried roadway with medium‐hard surrounding coal/rock. Stress criterion and energy criterion for rock burst occurrence were proposed according to the three types of roadways. The rock bursts that occurred in stope 32 of Gucheng coal mine in China agree well with the calculation results. Finally, an active rock burst preventive approach (long borehole destress drilling) is suggested before intense supporting measures are adopted during roadway construction to prefracture the coal seam or competent strata. The efficiency of this method at different excavation stages is evaluated by examining borehole drill cuttings. The whole roadway was excavated without any rock burst after the borehole destress drilling method was implemented.

Formation mechanism of a rainfall triggered complex landslide in southwest China

This case study is about a landslide that occurred after 4 days of heavy rainfall, in the morning of June 29, 2012, in Cengong County, Guizhou Province of China, geographical coordinated 108°20′-109°03′E, 27°09′-27°32′N, with an estimated volume of 3.3×106 m3. To fully investigate the landslide process and formation mechanism, detailed geotechnical and geophysical investigations were performed including borehole drilling, sampling, and laboratory tests coupled with monitoring of displacement. Also, a combined seepage-slope stability modeling was performed to study the behavior of the landslide. After the heavy rainfall event, the sliding process started in this area. The landslide development can be divided into different parts. The man-made fill area, spatially distributed in the south side of the landslide area with low elevations, slid first along the interface between the slope debris and the strongly weathered bedrock roughly in the EW direction. Consequently, due to severe lateral shear disturbance, the slope in the main sliding zone slid next towards the SW direction, along the sliding surface developed within the strongly weathered calcareous shale formation located at a depth of 25-35 m. This means it was a rainfall triggered deep-seated landslide. Finally, retrogressive failure of a number of upstream blocks occurred, which moved in more than one direction. The initial failure of the man-made fill area was the ‘engine’ of the whole instability framework. This artificial material with low permeability, piled up in the accumulation area of surface and sub-surface and destroyed the drainage capacity of the groundwater. The numerical modeling results agreed with the analysis results obtained from the laboratory and field investigations. A conceptual model is given to illustrate the formation mechanism and development process of the landslide.

Characterizing subseismic faults from SK-2 drilling core (2900–4200 m): Implication for reservoir transmissibility and regional tectonic evolution

Undiscernible faults on seismic reflection profiles are referred to as subseismic faults. Although most subseismic faults are undetected, they play a significant role in understanding regional tectonic evolution and can influence the flow of oil and gas. The Songliao Basin in northeast China is a typical Meso-Cenozoic continental petroliferous basin characterized by stable sedimentation, rift-depression dual structure, and large-scale oil and gas production. However, the characteristics of subseismic faults and their effect on petroleum resources remain not well understood. We have examined findings from the SK-2 east borehole located in the Songliao Basin, which is the deepest (7018 m deep below the ground surface) continental scientific drilling borehole in East Asia. We identified 46 subseismic faults at 2900–4200 m depths based on the observations of core-scanning images, macro- and microstructures, and well-logging data. Macro- and microstructural analyses indicate that most of the subseismic faults in the borehole indicate normal slip. These observations suggest that these subseismic faults may form in response to regional extension in the Shahezi (K1sh) period. The cross-cutting relationships among several groups of sheared fault planes or elongated veins filled in the fractures likely reflect multistage faulting. The subseismic faults are considered to be related to the nearby larger scale faulting as interpreted on the seismic profile. The spatial correlation between the observed subseismic faults and elevated hydrocarbon concentrations documented by borehole mud gas logging suggests that the subseismic faults might have controlled gas migration in the study area.

Experimental Investigation of Drilling Lateral Boreholes in Chalk Rocks with High-Pressure Jets

Increasing reservoir connectivity to the wellbore and bypassing the damaged area is crucial in improving the productivity of the wells and enhancing the swept area. This has become feasible by a new technology called radial jet drilling (RJD), in which relatively long, small-diameter laterals can be drilled radially from the main wellbore. In this study, the authors attempt to gain a better understanding of the efficiency of a high-velocity jet drilling on chalk destruction, and also identify parameters controlling the jet drilling. For this purpose, two distinct outcrop chalks from Austin, Texas (US) and Northern Province, Welton (UK) are used in this study, which are analogs to the reservoir chalk in the North Sea. In conjunction with the jet drilling experiments, basic rock mechanics testing is carried out in order to correlate the rock strength and stiffness properties to the jet drilling performance. Jet drilling of boreholes is evaluated not only by varying the fluid and nozzle type and the fluid pressure at the nozzle, but also varying the jet drilling setup under unconfined and also confined stress fields resembling reservoir condition. Results of our study show a clear correlation of the rock strength (and stiffness) on the threshold pressure and specific energy required to break the rock. Tight chalk requires more than 30% higher pump pressure than used in soft chalk for breaking the chalk, having more than twice the strength properties. Soft chalk presents larger borehole size and better rate of penetration, both with water and acid-aided fluid, owing to its higher matrix permeability value, as well as lower mechanical properties that favor diffusion of the jet drilling fluid into the rock and faster erosion/breakage compared with tight chalk. Static nozzles create a larger surface area compared with rotating nozzles. The penetration rate of the nozzle is improved significantly under stress confinement. In addition, jet drilling in the direction of minimum principal stress (σ3) appears to be faster owing to localization of shear failure around the drilled hole induced by the differential stresses compared with the jet drilling in the direction of maximum principal stress (σ1) under isotropic stress or ambient conditions.

Tree-Type Boreholes in Coal Mines for Enhancing Permeability and Methane Drainage: Theory and an Industrial-Scale Field Trial

Tree-type borehole drilling (TTBD) is a novel stress relief method for stimulating methane drainage from coal in underground coal mines. This paper is a report on studies that analyzed the permeability enhancement capabilities of tree-type boreholes in coal seams and presents a precedent-setting industrial trial of this new method in a 200-m section of a drainage roadway in a coal mine, the Shoushan coal mine in Henan province, China. Detailed simulation results indicated that after coal seams were stimulated using the TTBD method, a large number of fractures were initiated around the tree-type boreholes. These fractures propagated along the direction of maximum horizontal stress and formed highly permeable flow channels for methane transport from the coal into the tree-type sub-boreholes. The fractures gradually became shorter along the length of the sub-boreholes. As the sub-boreholes were shortened, the area fractured and the number of induced fracture decreased rapidly. Conversely, the fracture density and the value of homogeneity coefficient, β, increased. The industrial trial showed that compared with gas drainage from a conventional borehole in the Ji15−17 coal seams, the gas production rate from a single tree-type borehole was 4.7 times faster and the percentage of methane in the gas produced was 1.7 times higher. In addition, the borehole drainage attenuation time was 2.5 times longer for the tree-type boreholes. The total volume of gas production produced from 238 tree-type boreholes in a 200-m section of roadway was over 70,000 cubic meters, 1.4 times the methane extracted by 938 conventional boreholes in an adjoining 200-m section of the same roadway. In addition, the number of boreholes required to drain 1.4 times as much gas was 75% smaller. These results have provided support for the appreciation and application of this new technique for improving underground coal mine methane drainage.

CLOTTING NOMADIC SPACES: ON SEDENTISM AND NOMADISM

Abstract With reference to Jeffrey C. Kaufmann’s concept of a ‘sediment of nomadism’, for which pastoralism is still, implicitly or not, referenced and essentialised to ‘pure’ degrees of mobility and ‘pure’ food economies centred around livestock, this article argues that, in pastoral settings, sedentism is equally essentialised. This article reverses the traditional critique of the nomadism/sedentism dichotomy by questioning the relevance of ideal types of ‘pure sedentism’. Based on fourteen months of ethnographic fieldwork in the Northern Kenya arid lands, this article looks away from big cities and regional urbanities to focus on small settlements springing up along improved roads and telecommunications infrastructure, showing that places are never motionless, despite measures of emplacement promoted by national and local governments and the international community. The drilling of boreholes, the construction of health centres and schools, the distribution of aid does not stop the mobility of places nor of their inhabitants. Until places remain mobile, they are alive; otherwise they clot. This argument makes it possible to move beyond a dichotomic definition of sedentism and nomadism to value changes, flexibility, and plasticity as important features of places created and recreated by mobile pastoralists.

Deformation characteristics and failure mechanism of a reactivated landslide in Leidashi, Sichuan, China, on August 6, 2019: an emergency investigation report

At approximately 2:00 p.m. (Beijing time) on August 6, 2019, the previously controlled Leidashi landslide was reactivated near group 7 of Zhangjiagou village, Jianyang County, Sichuan Province, China. The 2019 Leidashi landslide damaged two main roads and 44 antisliding piles and posed a threat to another main road. This landslide was a reactivation of the 2010 Leidashi landslide and had an accumulation zone of 2.2 × 106 m3. To explore the deformation characteristics and failure mechanism, detailed field investigations, unmanned aerial vehicle photogrammetry, airborne LiDAR surveys, borehole drilling and inclinometer installation were carried out, and the collected data were analyzed. The results show that the 2019 Leidashi landslide could be divided into main slipping zone and activated zone according to movement state, and the main slipping zone could also be divided into main scarp area, main deposit area, climbing area, uplift area, and local landslide area according to the local movement and geomorphic features. The rapidly increasing landslide thrust caused by short-term but continuous heavy rain caused the failure of the antisliding piles and ultimately reactivated the 2010 landslide.

Imaging the active faults with ambient noise passive seismics and its application to characterize the Huangzhuang-Gaoliying fault in Beijing Area, northern China

Most serious geotechnical problems related to rock engineering are generated by the existence of faults. Detection of fault (especially active faults) is the first step to conduct any further in-depth studies in faulted rock mass or rock blocks. In this paper, we investigated the plausibility to image fault zones by passive seismic surveys using recorded ambient noise. The test site is in the north suburb of Beijing, northern China along the south bank of the northwest-southeast running Wenyuhe River, where the NNE-striking Huangzhuang-Gaoliying fault (HGF, active in the Holocene) is crossing. In general, the results are in good agreement with previous studies using active source seismics conducted in this area along the HGF and existing borehole drillings in the vicinity. Undoubtedly, Active source seismic reflection technique is the best technique to image fault in depth with high resolution. The drawback is its high cost and the necessity of using explosives, a practice usually prohibited in urban settings. In contrast, passive seismic surveys take the advantage of the ever-existing ambient noise source, and provide a low-cost technique, and fast deployment that can locate the fault effectively. Though the imaging resolution is lower compared to those obtained by active source seismic surveys, our passive seismic experiment at the Wenyuhe River site demonstrated that this approach is effective, especially for those faults with significant normal faulting component and the stratigraphy is significantly different on the two sides crossing the fault line.