Geological Fault Zones Research Articles

Methods of finding and developing underground water resources

The paper presents the methods of finding for underground water resources using the observation method of the natural impulsive electromagnetic field of the Earth and substantiates the technology of drilling water wells using the down-the-hole drilling method. The most promising sources for extracting of high-quality drinking water, namely fractured water, are considered. It is shown that these methods can be applied in mining areas with an open type of mineral development in the crystalline rocks of the Ukrainian Shield, given the strength of the rocks in geological fault zones, which exceeds f=10 on Professor Protodyakonov’s scale. Previously, water resources in such collector formations were not considered promising due to the difficulty of drilling. The flow rate for water is directly proportional to the final diameter of the drilling wells, that is, the larger the final diameter of the well, the larger the diameter of the filtration column that can be installed, and the greater the discharge that can be obtained. Therefore, equipment with diameters of 200 mm and larger is used for water wells construction.

Numerical simulation of spatial temperature and salinity distribution in the Waiwera geothermal reservoir, New Zealand

The geothermal reservoir in Waiwera was not sustainably managed for many decades. Hence, the responsible authority introduced a water management concept, whereby various independent models were developed and calibrated using observations. As these models were not yet able to reproduce all observations, constant model revisions are critical for efficient reservoir management. Results of a recent field campaign were used for the current model revision, considering two new main structural geological findings to reconstruct the natural reservoir state. Our simulation results demonstrate that a recently proven north-south trending fault in the study area plays a key role in improving the model. Further analysis suggests the presence of a not yet confirmed additional west-east aligned geologic fault in the north, since thermal convection is observed inland. Additional field campaigns are needed to acquire more information on the main geological fault zones as well as additional data on temperature and salinity distributions.

Update for reactive transport modeling of the Kızıldere geothermal field to reduce uncertainties in the early inspections

The development of carbon capture and storage techniques has become essential to reduce and mitigating CO2 emissions to the atmosphere. CarbFix1 and CarbFix2 projects carried out in Iceland demonstrated that the emissions of waste CO2 gas from geothermal power plants can be captured and mixed with the effluent geofluid and subsequently injected back into the geothermal reservoir. This experience gained in the CarbFix projects expanded into other geothermal fields around Europe, and one of the demonstration sites is the geothermal field in Turkey, Kızıldere. This paper focuses on the results of an updated study on early field evaluations with reactive transport simulations. In the new three-dimensional numerical model, the geological formations and fault zones were updated according to the well-logs data. Based on the tracer tests performed in the field, the anisotropic permeabilities between the wells were evaluated and imposed into the model. Geofluid chemistry, mineral components, and the volume fractions used as input in the simulations are modified depending on the performed laboratory experiments on the metamorphic schists taken from the geothermal site (i.e. X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning-electron microscope (SEM), and batch reactor tests). Different thermodynamic databases such as Lawrance Livermore National Laboratory (LLNL) and Thermoddem databases were tested using PHREEQC and TOUGHREACT programs for consistency with experiments. The thermodynamic conditions and the geofluid-rock-CO2 interactions prevent the mineralization of CO2 in the reservoir. This outcome differs from CarbFix projects in terms of the carbonization process, but the CO2 injection is still reliable with solubility-trapping in a geothermal reservoir to partially mitigate the emission. Roughly, 200 kt of CO2 in 10 years can be safely injected into the geothermal reservoir. According to the new analysis, the ratio of magnesium, sodium, and potassium varies in solid solution series of feldspars and clay minerals as albite end-member and montmorillonite/illite end-members, respectively. The evaluations of solid solution reactions are relatively limited in the law of mass action approach used by PHREEQC and TOUGHREACT.

Magnetic and gravity modeling and subsurface structure of two geothermal fields in the UAE

There are two low-enthalpy geothermal systems along the eastern border of the United Arab Emirates: Ain Khatt (Khatt City, Ras Al Khaimah Emirate) and Green Mubazzarah–Ain Faidha (GMAF) (Al-Ain City, Abu Dhabi Emirate). The hot springs are likely to be meteoric waters fed through deep-seated faults that intersect the geothermal reservoirs at 2.6–3.8 km depth. Gravity and magnetic data were analyzed by gradient (horizontal derivative “HD”, and improved normalized horizontal tilt angle “INH”), and separately 3D modeled to image the subsurface structure of the two UAE geothermal systems. Bouguer anomalies in GMAF and Ain Khatt range from − 14.2 to 8.09 mGal and − 169.3 to − 122.2 mGal, respectively. Magnetic intensities in GMAF and Ain Khatt vary from 39,327 to 44,718 nT and 43,650 to 44,653 nT, respectively. The UAE hot springs (GMAF and Ain Khatt) are located in mainly high HD and INH regions, which reflect significant discontinuities in the basement rock, such as faults or lithological contacts. A joint inversion of magnetic and gravity data, through Artificial Neural Network (ANN) modeling, was performed to explore and interpret the 3D density and magnetic susceptibility variations. Results show that the hot springs in both geothermal systems are associated with intersecting geological contacts and fault zones. The Green-Mubazzarah–Ain Faidha hot springs may be connected at depth.

Determination of Background Concentrations of Ag, Pd, Pt and Au in Highly Mineralized Ground Waters at Sub-ng L-1 Concentrations by Online Matrix Separation/Pre-Concentration Coupled to ICP-SFMS.

Though not regulated in directives such as the Water Framework Directive of the European Union, the investigation of geogenic background concentrations of certain elements such as precious metals is of increasing interest, in particular for the early detection of a potential environmental pollution due to the increased use in various industrial and technological applications and in medicine. However, the precise and accurate quantification of precious metals in natural waters is challenging due to the complex matrices and the ultra-low concentrations in the (sub-) ng L−1 range. A methodological approach, based on matrix separation and pre-concentration on the strong anion exchange resin TEVA® Resin in an online mode directly coupled to ICP-SFMS, has been developed for the determination of Ag, Pt, Pd and Au in ground water. Membrane desolvation sample introduction was used to reduce oxide-based spectral interferences, which complicate the quantification of these metals with high accuracy. To overcome errors arising from matrix effects—in particular, the highly varying major ion composition of the investigated ground water samples—an isotope dilution analysis and quantification based on standard additions, respectively, were performed. The method allowed to process four samples per hour in a fully automated mode. With a sample volume of only 8 mL, enrichment factors of 6–9 could be achieved, yielding detection limits <1 ng L−1. Validation of the trueness was performed based on the reference samples. This method has been used for the analysis of the total concentrations of Ag, Pt, Pd and Au in highly mineralized ground waters collected from springs located in important geological fault zones of Austria’s territory. Concentrations ranges of 0.21–64.2 ng L−1 for Ag, 0.65–6.26 ng L−1 for Pd, 0.07–1.55 ng L−1 for Pt and 0.26–1.95 ng L−1 for Au were found.

Seismic Risk Assessment of Chania, Greece, Using an Integrated Computational Approach

This study develops a comprehensive seismic risk model for the city of Chania, in Greece, which is located ina highly seismic-prone region due to the occurrenceof moderate to large earthquakes because of the nearby major subduction zone between African and Eurasian tectonic plates. The main aim is to reduce the seismic risk for the study area by incorporating the spatial distribution of the near-surface shear wave velocity model and the soil classification, along with all possible seismic sources, taking into account historical events. The study incorporates and correlates various ground motion scenarios and geological fault zones as well as information on existing buildings to develop a seismic risk model using QuakeIST software, and then the seismic hazard and a realistic prediction of resulting future adverse effects are assessed. The developed model can assist the municipal authorities of Chania to be prepared for potential seismic events, as well as city planners and decisionmakers, who can use the model as an effective decision-making tool to identify the seismic vulnerability of the city buildings and infrastructure. Thus, this study enables the implementation of an appropriate and viable earthquake-related hazards strategy to mitigate damage and losses in future earthquakes.

Potential of hydraulic tomography in exploring the preferential flowpaths of water inrush in coal mine areas

Water inrush is a major hidden danger that decreases coal mining safety. Thus, preferential flowpaths of water inrush in mining areas must be investigated to prevent water disasters and guide grouting engineering. In this study, pumping and observation data of five boreholes were input into a 2D groundwater flow model established using VSAFT2 software for inversion to obtain the heterogeneous distribution information of the site. Then, the wide-field electromagnetic method was used to obtain the distribution of resistivity values at different depths in the local area. Finally, we compared and analyzed the relevant geological information of the site, such as the fault zones and karst collapse columns, obtained using the above two methods to determine the preferential flowpaths of water. The results show that (1) the hydraulic conductivity distribution estimated by hydraulic tomography is consistent with the location distribution of high-resistivity and low-resistivity areas identified by the wide-field electromagnetic method; (2) the high hydraulic conductivity zones obtained by hydraulic tomography are consistent with the known distribution of geological fault zones, which is important because water inrush accidents often occur in areas where fault zones exist; and (3) based on the comprehensive analysis of the above results, a preferential flowpaths of water inrush was identified. The flowpaths starts from the F35 fault zone, passes through KCC2, converges with the water from the middle part of fault zones F11 and F12, and finally supplies Dongfeng well D1. This paper compares HT results to resistivity estimates from independently conducted geophysical surveys. The identification of the groundwater flow pathway through HT can help to minimize future water in-rush accidents.

Suitability of Underground Space Development in Plateau Cities Based on Geological Environment Analysis: Case Study in Kunming, China

Geology forms the basis for underground space development. In mountainous plateau areas, developing underground spaces requires detailed analyses and appraisal. This study used the index scale analytic hierarchy process (AHP) to analyze the geological conditions and to propose an evaluation system suitable for Kunming, China. An evaluation model was established using mathematical principles, and a geological suitability evaluation of Kunming was conducted using GIS. According to the evaluation, underground space in Kunming considered suitable, medium suitable, unsuitable, and forbidden for development accounts for 37.81%, 20.38%, 17.61%, and 24.2% of its total area, respectively. Soft soil and karst topographies are the primary disqualifying factors, followed by groundwater and geological fault zones. Our results reveal that most of the underground spaces in the plateau area are suitable for development. However, there are areas where construction should be strictly regulated, such as those adjacent to geological fault zones. With this study, the superiority of the index scale method was demonstrated, and the consideration criteria of the evaluation system and indexes in plateau cities were proposed.

Paleoseismic Slip Records and Uplift of the Longmen Shan, Eastern Tibetan Plateau

AbstractWe document the geological fault zone geometry and internal architecture of the Yingxiu‐Beichuan fault (YBF) in the Longmen Shan, eastern Tibetan Plateau, which hosted the catastrophic 2008 Wenchuan earthquake. The YBF has been repeatedly reactivated during its long‐term activity and contains widespread brittle fault rocks. Pseudotachylytes are recognized in the Pengguan Complex both from the Wenchuan earthquake Fault Scientific Drilling (WFSD) cores and at a surface outcrop. Microstructural evidence of embayed and rounded fragments, flow structures, vesicles, and microlites of various morphologies indicate that the pseudotachylytes were generated by frictional melting during earthquakes. Cataclasite and fault gouge with fragments of angular shapes and varied sizes observed within the fault zones are also considered as evidence of paleoearthquakes. These imply that the main fault zones in the WFSD cores record ancient seismic slip events. Geological field mapping at the surface and in WFSD cores shows that the YBF is a listric reverse fault, with a 155–290‐m thick fault zone that dips 73°–68° at depths &lt;700 m and 30° at depths &gt;700 m. Three faulted sets of alternating Neoproterozoic Pengguan Complex overthrusting upon the Late Triassic Xujiahe Formation in the WFSD‐2 core imply that the main tectonic framework of Longmen Shan consists of a series of imbricated thrust sheets that have accommodated strong crustal shortening. These suggest that the accumulated crustal shortening caused by imbricated thrusting and long‐term seismic activity along the YBF and deep concealed faults is an important process responsible for the rapid uplift of the Longmen Shan.

In‐situ assessment of strain behaviour inside tunnel linings using distributed fibre optic sensors

AbstractIn modern tunnelling, deformation monitoring is an important component to ensure a safe construction. It is state of the art to measure displacements at the inner side of the tunnel lining using total stations. In addition, pointwise geotechnical sensors, e.g. electric strain gauges, may be installed in geological fault zones, which, however, do not deliver a complete picture of the internal deformations. The Institute of Engineering Geodesy and Measurement Systems (Graz University of Technology) supported by the Austrian Federal Railways (ÖBB‐Infrastruktur AG, SAE Fachbereich Bautechnik/Tunnelbau) developed a fibre optic sensing system, which realizes thousands of measurement points inside the tunnel lining. The distributed measurements can be used to assess the in‐situ strain behaviour as well as to localize failures (e.g. cracks) in the lining. This paper reports about the calibration of the fibre optic system under well‐known laboratory conditions and the practical utilization of the system in mechanized and conventional tunnelling. The results demonstrate the high potential of distributed fibre optic systems and their capability especially in the operational phase to extend classical measurement methods in tunnelling projects.

Isolation by marine barriers and climate explain areas of endemism in an island rodent

AbstractAimThe Indonesian island of Sulawesi is home to thousands of endemic terrestrial animal species. Phylogeographical studies of some of these taxa revealed concordant distribution patterns (areas of endemism; AoEs), suggestive of a shared evolutionary or ecological mechanism driving divergence among various terrestrial taxa. Generally, AoEs have been attributed to Pleistocene marine incursions, geological fault zones and Sulawesi's history as an archipelago. We test, for the first time, the hypothesis that population divergences are associated with unsuitable climate spaces at the boundaries between these areas.LocationSulawesi, Indonesia.TaxonMaxomys musschenbroekii, a common murid rodent endemic to Sulawesi.MethodsWe sequenced a mitochondrial gene, four nuclear protein‐coding genes and hundreds of ultraconserved elements from individuals sampled across the island, which we used to build intraspecific phylogenies and identify population structure. To test climate‐related hypotheses, we used multiple regression to assess the extent to which genetic distances, over‐land geographical distances, environmental distances (derived from ecological niche model resistance surfaces) and areas of endemism are correlated.ResultsIn all three genetic datasets, we inferred phylogeographical structure that is geographically concordant with previously defined AoEs. Ecological niche models showed a similar geography of suitability across the island since the Last Glacial Maximum, with varying levels of unsuitable climate space between AoEs. Genetic distances were more strongly correlated with environmental distances than geographical distances and interspecific divergences arose just in the past 1.5 Myr.Main ConclusionsPopulation divergences within M. musschenbroekii are consistent with AoE definitions from other taxa. Stable areas of unsuitable habitat near AoE boundaries probably supplemented marine incursions in generating population structure within M. musschenbroekii and other co‐distributed species.

Geological Structures Mapping of Bukit Bunuh using 2-D Resistivity Imaging Method

The geological area of Bukit Bunuh is very complex due to the meteorite impact that has occurred millions years ago at Lenggong, Perak. The lithology of the study area consists of alluvium, tephra dust, and granitic rock. The geological contact, fault and fracture zone were found at the study area may indicate the geological process that undergoes at a place locally or regionally. These important features have led to the further research on 2-D resistivity imaging method (2-D RIM) to study the geological features. This method can provide the subsurface image that will delineate the geological structures. The surveys include three separate lines of different length which depend on the accessibility. The surveys were done by using Pole-Dipole array and 10 m of electrodes spacing. The objectives of this research are to determine the subsurface geological contact and to determine the existence of fault/fracture zones at the contact zone. The results from 2-D inversion profiles have successfully signified the types of geological structural such as fault, contact, and fractures. Hence, the results from 2-D RIM were used to draw the geological lineaments of Bukit Bunuh. The discontinuity of the lineaments may indicate the structures present.

Gloggnitz contract after completion of the intermediate access at Göstritz

AbstractThe intermediate construction access at Göstritz was planned based on the results of a comprehensive geological investigation programme. The intermediate access minimises the risk of the excavation of the Semmering Base Tunnel through the Grassberg‐Schlagl fault system, which is located in the Otterstock area in Lower Austria. The site consists of an approx. 1000 m long access tunnel, a complex system of shaft head caverns, two shafts with a depth of about 250 m down to the level of the tunnel as well as a system of shaft bottom caverns for the four tunnel drives in the directions of Gloggnitz and Mürzzuschlag. During the construction of the access tunnel, a new shaft head layout was proposed by the contractor in form of value engineering to optimize further construction operation, and the optimized layout was adopted to the contract. At the end of the access tunnel, it turned out that the shaft head cavern system could neither be constructed in the original layout as tendered nor in the newly revised layout due to a geological fault zone, which had not been predicted despite extensive geological investigation in advance. Consequently, ÖBB, designer and contractor worked intensively to find a new feasible design to enable further construction of the cavern system, avoid a standstill of tunnelling works and comply with all approvals.

INVESTIGATION OF POTENTIAL ALKALI-SILICA REACTIVITY OF AGGREGATE SOURCES IN THAILAND

Since the first local evidence of alkali-silica reaction (ASR) was reported in Thailand in 2011,awareness of ASR was raised and the importance of aggregate performance database was recognized, thus anattempt to set up local aggregate database was initiated. As part of the effort to establish the database, a studyof potential ASR reactivities was carried out involving aggregates from several current industrial sources ineastern and central Thailand and the results were presented here. Aggregate samples were randomly collectedfrom various sources and tested by two methods; accelerated mortar-bar test (AMBT) and petrographicexamination. The types of aggregate sampled included limestone, greywacke, and rhyolitic tuff. The AMBTexpansion results indicated that several aggregate types had larger expansion than the threshold of potentiallydeleterious ASR behavior as suggested by ASTM C 1260 standard. Furthermore, it was found that samples ofsame aggregate type, although apparently had mineralogically similar compositions, had different reactivities,particularly when sampled from around geological fault zone compared with that taken from the surroundingarea and portions of parent rock were observed to be weathered in this area. Thin section analysis revealedevidence of ASR gel at the aggregates’ rim, inside the aggregates and in the matrix. These findings suggestpossible future ASR problems in Thailand as well as in neighboring countries where the continuity ofgeology pattern is observed.

Earthquake swarms in Greenland

Two earthquake swarms have been detected in Greenland. One occurred on the island of Disko in August 2010, the other one was active from January 2008 to June 2009 near the South-East Greenland coast c. 200 km south of Tasiilaq. An earthquake swarm is defined as a series of earthquakes of similar magnitude located within a small area. The magnitude of the largest earthquakes in a swarm is typically less than 4 (Ma &amp; Eaton 2009). Swarm activity is distinctly different from the more common mainshock–aftershock activity, which is characterised by one large earthquake (mainshock) followed by a series of smaller aftershocks. Earthquake swarms mainly occur in areas with tectonic and/or volcanic activity (Stykes 1970), but intraplate swarms are also found in otherwise stable environments (Gregersen 1979; Atakan et al. 1994; Uski et al. 2006; Ma &amp; Eaton 2009). Geological boundaries and old fault zones appear to be a common setting for intraplate earthquake swarms. Earthquake swarms have previously been detected in North and North-East Greenland (Gregersen 1979) at a time when the seismograph coverage was very sparse. It was concluded that the earthquake swarms were caused by tectonic stresses in and around old sedimentary basins near the continental margin.

Fortune or misfortune: threats and opportunities for the development of the tourism industry in the heavily attacked area in '5.12' earthquake of China

The ‘5.12’ earthquake of China has caused extremely serious damage to the tourism industry in the earthquake area in SiChuan including LongMenshan geological fault zone. Tourism infrastructure and tourism attractions are all destroyed and visitors’ confidence is heavily hurt; on the other hand, high frequency and high intensity reports from medias over the world about disaster and disaster relief has greatly improved the area’s visibility, therefore, the tourism infrastructure can get improvements, and the tourist location greatly ascend. Threats and opportunities for the tourism industry in ecological reconstruction regions of LongMenshan geological fault zone are exist with each other. In this paper, we argue that restoration and reconstruction of tourism industry in Longmenshan geological fault zone after the disaster should be committed to such measures: enhancing the confidence of tourists, upgrading tourism products and industries, and overall planning the development of the tourism industry outside the region.

Infrasound produced by debris flow: propagation and frequency content evolution

Rapid mass movements such as avalanches, debris flows, and rock fall are periodic or episodic phenomena that occur in alpine regions. Recent studies have shown that debris flows generate characteristic signals in the low-frequency infrasonic spectrum (4–15 Hz). Infrasound can travel thousands of kilometers and can still be detectable. This characteristic provides a basis for the development of wide area automated monitoring systems that can operate in locations unaffected by the activity of the process. This study focuses on the infrasound vibrations produced by a debris flow at the Lattenbach torrent, Tyrol (Austria), and by two events at the Illgraben torrent, Canton of Valais (Switzerland). The Lattenbach torrent is a very active torrent, which is located in the west of Tyrol in a geologic fault zone between the Silvrettakristallin and the Northern Limestone Alps. It has a large supply of loose sediment. The Illgraben torrent, which is well known for its frequent sediment transport and debris flow activity, has been equipped with instruments for debris flow monitoring since the year 2000. This study shows that debris flow emits low-frequency infrasonic signals that can be monitored and correlated with seismic signals. During the passage of the debris flow, several surges were identified by ultrasonic gauges and detected in the time series and the running spectra of infrasonic data.

Geochemical variation of soil–gas composition for fault trace and earthquake precursory studies along the Hsincheng fault in NW Taiwan

The present study is proposed to investigate geochemical variations of soil–gas composition in the vicinity of the geologic fault zone of Hsincheng in the Hsinchu area of Taiwan. Soil–gas surveys have been conducted across the Hsincheng fault, to look for the degassing pattern of this fault system. During the surveys, soil–gas samples were collected along traverses crossing the observed structures. The collected soil–gas samples were analysed for He, Rn, CO 2, CH 4, Ar, O 2 and N 2. The data analysis clearly reveals anomalous values along the fault. Before selecting a monitoring site, the occurrence of deeper gas emanation was investigated by the soil–gas surveys and followed by continuous monitoring of some selected sites with respect to tectonic activity to check the sensitivity of the sites. A site was selected for long term monitoring on the basis of coexistence of high concentration of helium, radon and carrier gases and sensitivity towards the tectonic activity in the region. A continuous monitoring station was established at Hsinchu National Industrial Science Park (HNISP) in October 2005. Preliminary results of the monitoring station have shown possible precursory signals for some earthquake events.

Source zones of strong earthquakes in southern Yakutia as inferred from paleoseismogeological data

Investigations aimed at revealing traces of recent tectonic activity in geological fault zones were carried out in 2006 in the territory of southern Yakutia and the Amur region in connection with works on detailed seismic zoning of the route of the East Siberia-Pacific Ocean oil pipeline. In addition to geological-geomorphological and geophysical studies, the complex investigations included paleoseismogeological studies and were accompanied by the driving of mine workings through topographic forms that could be associated with zones of active tectonic disturbances. This approach made it possible to substantially refine the available information on seismotectonics and the potential seismic hazard of the region.

Two‐dimensional stable‐layered laboratory‐scale experiments for testing density‐coupled flow models

A series of laboratory‐scale two‐dimensional porous medium tank experiments was conducted to study stable‐layered variable density flow problems using well‐defined experimental parameters and boundary conditions. The experiments were carried out both in a rectangular flow tank and in a more complex geometrical setup aimed at studying variable density flow in geometries similar to geological formations of aquifers and aquicludes connected via fault zones. An impermeable layer within the porous medium tank forced the solutes to pass through a vertical channel, representing a geological fault zone, to reach the outlet of the tank. Flow through the porous medium occurred through a single inflow opening and an outflow opening on the opposite edge of the domain. An image analysis technique delivered 2%, 10%, 50%, and 80% salt concentration isolines at distinct times. Breakthrough curves of the dyed saltwater with an initial density of 1063 g/L were available at any location within the tank. The experimental data are presented as benchmark problems to evaluate numerical codes. A numerical model based on mixed finite elements for the fluid flow problem and a combination of discontinuous Galerkin finite element and multipoint flux approximation methods for the transport turned out to be adequate for the simulation of the physical experiments. The high data availability makes the proposed benchmark experiments a valuable tool for assessing the performance of density‐coupled flow models.