Earth Fissures Research Articles

Application of seismic prospecting to determine the width of influence of surface faults associated to land subsidence – a case of study in the Aguascalientes Valley, México

Abstract. Aguascalientes valley, located in the central part of México, is affected for a land subsidence process triggered by groundwater withdrawal since the 1980's. Currently, the occurrence and the reactivation of surface faults and earth fissures due to differential subsidence, is the main concern for government bureaus dealing with urban planning, because of the damages that these terrain discontinuities are able to cause in constructions and infrastructure. The deformation and rupture process produces an active linear discontinuity with a variable width of influence, where the constructions and infrastructure are prone to get damage. Therefore, the determination of this width of influence is critical for urban planning and hazard determination. In this work, the results of a geophysical seismic survey carried out in six surface discontinuities located in the subsidence area of the Aguascalientes Valley, are presented and discussed. The study included acquisition of seismic tomography profiles measured perpendicularly to the discontinuities, in order to obtain the P-wave velocity sections. The resulted P-wave velocity models show a low-velocity anomaly within the fracture trace with widths from 50 to 100 m. This anomaly is interpreted as a mechanically disturbed zone due to the activity of the surface fault, this is, due to the presence of fracturing caused to the adjacent material by the differential subsidence. The results suggest that the material in the disturbed zone, is experiencing a increase in secondary porosity, caused by the deformation and rupture process, and the subsequent generation of small fissures and voids. The results of this study have practical implications because the methodology allows defining the influence zone of an active discontinuity, and therefore, to establish a restricted width along the surface discontinuity. The definition of this restraint zone is a first step to produce a subsidence hazard zoning including not only the discontinuity trace but its width of influence.

Assessment of seismic damage on frame structures across the earth fissure under earthquake

An accurate evaluation of structural damage is essential to performance-based seismic design for the structure across the earth fissure. By comparing the calculation results from three commonly used damage models and the experimental results, a weighted combination method using Chen model was selected in this paper as the seismic damage evaluation. A numerical model considering the soil-structure interaction (SSI) was proposed using ABAQUS software. The model was calibrated by comparing with the experimental results. The results from the analysis indicated that, for the structure across the earth fissure, the existence of earth fissure changed the damage distribution of the structural members. The damage of structural members in the hanging wall was greater than that in the foot wall. Besides, the earth fissure enlarged the damage degree of the structural members at the same location and changed the position of the weak story. Moreover, the damage degree of the structure across the earth fissure was greater than that of the structure without the earth fissure under the same excitation. It is expected that the results from this research would enhance the understanding of the performance-based seismic design for the structure across the earth fissure.

The dynamic response of sites with earth fissures as revealed by microtremor analysis——A case study in the Linfen Basin, China

Earth fissures are a major cause for concern worldwide, and an ever-increasing number of geohazards are being caused by fissures. However, the dynamic response of sites with earth fissures is still unclear. With the aim of providing previously lacking advice regarding earthquake fortification in proximity to fissures, this study employed microtremors to estimate the effect of fissures on the dynamic response of a site, taking fissures in the Linfen Basin as its example. Survey lines were laid across four earth fissures in three different regions: the Linfen depression, the Houma depression, and the piedmont of Lvliang Mountain. The time-history acceleration of microtremors was transformed into the Fourier amplitude spectrum, response acceleration, Arias intensity, and H/V spectral ratio. The results show that the frequency contents, including the spectral pattern, bandwidth, and spectral area, are consistent with the conditions in each region. The Fourier amplitude, peak acceleration, Arias intensity and H/V ratio amplitude are significantly elevated near the fissure, falling to the background value by 20 m away from it, whereas the predominant frequencies are independent of distance from the fissure. This change in the amplification factors confirms that earth fissures amplify the dynamic response of the site. A larger range of influence and greater amplification were detected on the hanging side of the fissure. Results from different regions show that the amplification and range of influence vary between regions. On the basis of the results, it is suggested that a higher seismic fortification intensity and a greater setback distance should be adopted at sites with earth fissures.

Characteristics and main causes of earth fissures in northeastern Beijing Plain, China

Earth fissures (EF) form in the northeastern Beijing Plain, causing horizontal and vertical displacements of the ground surface and damaging hundreds of buildings and roads. In addition, since 2009, an unprecedented number of cracks with vertical offsets have occurred in the Beijing Capital International Airport (BCIA), which is the busiest airport in China, causing serious financial losses and increasing the risk of air travel. The EF were divided into three groups, including EF1, EF2, and EF3, based on their distribution and deformation patterns. In general, the EF1 and EF2 fissures formed along segments of the NE-SW trending regional normal faults and have large vertical offsets but small widths. The deformation patterns, trenches and geophysical prospecting profiles, demonstrate that the EF1 and EF2 fissures propagated from the preexisting faults. In contrast, the EF3 fissures formed in a disorganized pattern above the paleochannels of the Chaobai River with short lengths and negligible vertical offsets. The monitoring data for the EF1 fissures indicates that the formation and deformation of the EF in the northeastern Beijing Plain were induced by groundwater pumping. The formation processes of the EF1, EF2, and EF3 fissures are classified into two categories: (1) on the existence of preexisting normal faults and (2) on the existence of paleochannels. Two hypothetical conceptual models are presented to illustrate the formation processes.

Characteristics and mechanisms for origin of earth fissures in Fenwei basin, China

The most serious earth fissure disasters in China occur in the Fenwei basin. Since the late 1950s, earth fissure disasters have widely occurred in the Weihe, Yuncheng, Linfen, Taiyuan, and Datong sub-basins in the Fenwei basin, and such disaster has increased progressively in recent years. The current paper summarizes the characteristics of earth fissures in the Fenwei basin. Earth fissures usually occur in an extensional faulted basin, along an active fault zone, and within an area of land subsidence. Earth fissures often have a similar trend, with many branches that intermittently appear along their strike. The main and secondary earth fissures at a shallow depth form rupture belts of different widths, but they merge into a single shear belt and stay connected with the underlying active fault. The throw of two blocks increases with depth along a sedimentary fault. Earth fissures usually show the characteristic of three-dimensional movement. Vertical dislocation is the primary aspect of earth fissure movement. The horizontal tension is smaller and the horizontal twist is the smallest, which is consistent with the movement pattern of underlying active faults. Earth fissures have exhibited activity three or four times since the late Pleistocene. In the past half-century, earth fissures formed during four or five periods of peak activity were influenced strongly by groundwater fluctuation. Our research also indicates that cluster formation of earth fissures is polygenetic and results from a combination of tectonic and human activities. Earth fissures are driven by deep tectonic motions beneath the basin and are controlled by the local tectonic stress of the local fault zones. One of the most important factors contributing to earth fissure formation is groundwater overexploitation. This paper provides a scientific basis for proposed administrative means, mitigation measures and engineering solutions in the field of engineering geology.

Discrete element method-based prediction of areas prone to buried hill-controlled earth fissures

An independently developed discrete element code, MatDEM, was used to simulate buried hill-controlled earth fissures. An initial cubic discrete element method (DEM) model was obtained by considering the gravity accumulation of particles. A 2D stratigraphic model can be constructed by importing an elevation table of different strata into a cubic model. A simplified fluid-structure interaction method was then introduced to this. The model was simulated by gradually lowering the water level and then calculating the compression deformation of strata. By comparing the calculated settlement to the monitoring data, the validity and accuracy of the MatDEM model were verified. The area prone to earth fissures was predicted based on the analysis of the particle connections and horizontal displacement. The formation mechanism of the buried hill-controlled earth fissures was also explained. Thus, MatDEM is a good numerical simulation method for studying discontinuous problems, such as rock and soil cracking, and can be a new tool with which to study earth fissures.

Earth fissure hazard prediction using machine learning models

Earth fissures are the cracks on the surface of the earth mainly formed in the arid and the semi-arid basins. The excessive withdrawal of groundwater, as well as the other underground natural resources, has been introduced as the significant causing of land subsidence and potentially, the earth fissuring. Fissuring is rapidly turning into the nations’ major disasters which are responsible for significant economic, social, and environmental damages with devastating consequences. Modeling the earth fissure hazard is particularly important for identifying the vulnerable groundwater areas for the informed water management, and effectively enforce the groundwater recharge policies toward the sustainable conservation plans to preserve existing groundwater resources. Modeling the formation of earth fissures and ultimately prediction of the hazardous areas has been greatly challenged due to the complexity, and the multidisciplinary involved to predict the earth fissures. This paper aims at proposing novel machine learning models for prediction of earth fissuring hazards. The Simulated annealing feature selection (SAFS) method was applied to identify key features, and the generalized linear model (GLM), multivariate adaptive regression splines (MARS), classification and regression tree (CART), random forest (RF), and support vector machine (SVM) have been used for the first time to build the prediction models. Results indicated that all the models had good accuracy (>86%) and precision (>81%) in the prediction of the earth fissure hazard. The GLM model (as a linear model) had the lowest performance, while the RF model was the best model in the modeling process. Sensitivity analysis indicated that the hazardous class in the study area was mainly related to low elevations with characteristics of high groundwater withdrawal, drop in groundwater level, high well density, high road density, low precipitation, and Quaternary sediments distribution.

Land subsidence susceptibility assessment using random forest machine learning algorithm

The mechanism of land subsidence and soil deformation deals with the dissipation of excess pore water pressure and the compaction of soil skeleton under the effect of natural or man-made factors, which can lead to serious disasters in the process of urbanization. The negative effects of land subsidence include structural and fundamental damages to underground and aboveground infrastructures such as pipelines and buildings, changes in land surface morphology, and creation of earth fissures. Arid and semi-arid countries like Iran are highly prone to land subsidence phenomenon. In these regions, precipitation rate and natural recharges are relatively lower than those of the global average showing the importance of ground waters for agricultural and industrial activities. Land subsidence has already occurred in more than 300 plains in Iran. Semnan Plain is one of the most important areas facing this phenomenon. The purpose of this research was to assess land subsidence susceptibility using random forest machine learning theory. At first, prioritization of conditioning factors was done using random forest method. Results showed that distance from fault, elevation, slope angle, land use, and water table have the greatest impacts on subsidence occurrence. Then land subsidence susceptibility map was prepared in GIS and R environment. The receiver operating characteristic curve was applied to assess the accuracy of random forest algorithm. The area under the curve by value of 0.77 showed that random forest is an acceptable model for land subsidence susceptibility mapping in the study area. The research results can provide a basis for the protection of environment and also promote the sustainable development of economy and society.

A typical Earth fissure resulting from loess collapse on the loess plateau in the Weihe Basin, China

Earth fissures are major geological hazards that frequently occur in the Weihe Basin in northwestern China and can cause severe damage to infrastructure. This paper reports a case study of earth fissures resulting from loess collapse in the village of Xibai, in the Weihe Basin. A series of geological investigations, consisting of a site investigation, trench excavation, geological drilling, exploratory well drilling, and geotechnical testing, were conducted to determine and analyze the characteristics of the Xibai Village earth fissures, as well as the physical characteristics of the loess in the earth fissure development area. The earth fissures were parallel to the village sewage pit and had a total length of 800 m. With a maximum depth of 8.5 m, the Xibai Village earth fissures were nearly vertical. Comparing the results of self-weight collapsibility coefficient and three parameters (void ratio, dry density, and water content) of loess at different distances from the sewage pit, the collapsibility of Malan loess in this area and the effects of leakage from the sewage pit were determined. The results revealed that a tilted seepage line was generated, and the loess below this seepage line underwent varying degrees of self-weight collapse deformation. The nonuniform collapse settlement and rotation deformation of loess above the seepage line were thus generated, while tensile stress was created in the upper part of the loess. This rotation of loess, similar to the deformation of the cantilever beam, caused the formation of the earth fissures at the site with higher tensile stress. Based on the rotation mechanism, this study explained the development process of collapse earth fissures and predicted that the Xibai Village earth fissures would continue to develop outward in the future.

IGCP 641 Project: Mechanisms, Monitoring and Modeling Earth Fissure Generation and Fault Activation due to Subsurface Fluid Exploitation

IGCP 641 Project: Mechanisms, Monitoring and Modeling Earth Fissure Generation and Fault Activation due to Subsurface Fluid Exploitation

Deformation Monitoring of Earth Fissure Hazards Using Terrestrial Laser Scanning.

Deformation monitoring is a powerful tool to understand the formation mechanism of earth fissure hazards, enabling the engineering and planning efforts to be more effective. To assess the evolution characteristics of the Yangshuli earth fissure hazard more completely, terrestrial laser scanning (TLS), a remote sensing technique which is regarded as one of the most promising surveying technologies in geohazard monitoring, was employed to detect the changes to ground surfaces and buildings in small- and large-scales, respectively. Time-series of high-density point clouds were collected through 5 sequential scans from 2014 to 2017 and then pre-processing was performed to filter the noise data of point clouds. A tiny deformation was observed on both the scarp and the walls, based on the local displacement analysis. The relative height differences between the two sides of the scarp increase slowly from 0.169 m to 0.178 m, while no obvious inclining (the maximum tilt reaches just to 0.0023) happens on the two walls, based on tilt measurement. Meanwhile, global displacement analysis indicates that the overall settlement slowly increases for the ground surface, but the regions in the left side of scarp are characterized by a relatively larger vertical displacement than the right. Furthermore, the comparisons of monitoring results on the same measuring line are discussed in this study and TLS monitoring results have an acceptable consistency with the global positioning system (GPS) measurements. The case study shows that the TLS technique can provide an adequate solution in deformation monitoring of earth fissure hazards, with high effectiveness and applicability.

Earth fissures developed within collapsible loess area caused by groundwater uplift in Weihe watershed, northwestern China

Earth fissures are geological hazards that frequently occur all over the world and greatly threaten the safety of people’s property and lives. This paper reports a case from a typical agricultural town in the Weihe watershed, northwest (NW) of China, Dali, which has been severely affected from earth fissures in recent years. A comprehensive survey was made on the geometric characteristics of the earth fissures developed in the study area through field investigations, trial trenches, boreholes, exploratory wells, and laboratory tests. The study indicates that fourteen nearly parallel fissures have developed in the area, with a fissure to fissure space of 140–350 m, and a maximum length of any of the given fissures of 500 m. The underlying faults, loess joints, and the Quaternary unconsolidated and collapsible sedimentary loess provide a favorable geological condition for the occurrence of the earth fissures. From 2003 to 2012, the groundwater level in the area rose about three meters due to agricultural irrigation and leakage of a water diversion canal. Collapsible deformation occurred in the loess, while seepage erosion expanded the original joints in the soil. The earth fissures occurred resulting from multiple geological environmental forces and human activities.

Active surface deformations detected by precise levelling surveys in the Afyon-Akşehir Graben, Western Anatolia, Turkey

In the actively deforming region of western Anatolia, crustal deformation is accommodated by destructive earthquakes and a variety of aseismic events. In this study, we investigated the 2016–2017 aseismic sequence located in the Bolvadin Fault, one of the segments of the Akşehir-Simav Fault System of western Anatolia by analysing surface deformation derived from detailed geological mapping. Our findings suggest that surface deformation in the Bolvadin Fault is accommodated by aseismic episodes. During the field studies in the Bolvadin area, progressive surface deformations, such as surface faults and earth fissures with a length of 800 meters to 3 kilometres and strike of N15°E to N70°E were mapped on a 1/5000 scale. Furthermore, a levelling network was established to calculate the vertical displacements and deformation rate along the surface deformations. Precision level measurements were undertaken in 2016 and 2017. On the routes to the NW of the Bolvadin settlement, a vertical deformation rate of 30 mm/yr was detected in the period of 2016–2017, and a large deformation rate of 40 mm/yr was detected in the same period.

Experimental study on Su-Xi-Chang earth fissures induced by repeated groundwater pumping and impounding

Surface subsidence and fissures, especially surface fissures, are typical geological disasters related to groundwater activities in the Su-Xi-Chang area, China. In this study, we first analysed the geologic background and hydraulic features of earth formation in the area and constructed a physical model and its related experimental system in the laboratory. Based on the model and the system, we further experimentally studied and theoretically analysed the mechanism of ground fissure formation. The results showed that development of the earth fissures obviously undergoes the following stages. First, under self-gravity, the soil (artificial sand) layers in the model box with larger void ratios are gradually compacted, leading to uneven surface subsidence. Second, although the excess pore-water pressure could cause the surface to rise locally and macroscopically, water impounding on the aquifer lowers the friction among sand grains to certain degree depending on the strength of seepage in the horizontal direction, resulting in surface deformation and subsidence. Third, strong water pumping instantaneously releases excess pore-water pressure, resulting in soil consolidation in the vertical direction. Therefore, repeated groundwater impounding and pumping together with unique geological conditions lead to the formation of earth fissures in the Su-Xi-Chang area.

Paleochannel-controlled earth fissures in Daming, North China Plain and their implication for underground paleogeomorphology

Earth fissures are a geologic phenomenon that mainly affects the medium with shallow surface soil and mainly developed in the Quaternary sediment cover. In the Yellow River-Qinghe River - Zhanghe River shallow buried paleochannel Band (HQZ-Qh2-II Band) on the North China Plain, 93 earth fissures are developed. Among them, 29 fissures are evolved in the Daming zone in the upper reaches of the paleochannel band. Thus, the zone belongs to a densely grouped fissure area. This study, through a series of field trenching and surveying, revealed that these earth fissures have unique plane distribution rules and profile structure features of short length (several meters to several hundred meters), shallow depth (smaller than 10 m) and good correspondence to Daming paleochannels. These basic characteristics reveal that unlike other tectonic earth fissures, Daming earth fissures are a new and unknown type of fissures, i.e., paleochannel-controlled earth fissures. Theoretical analysis of their features showed that they were formed due to the actions of gravity, primary joint factors and groundwater pumping activities and controlled by ancient river factors including paleochannels, sediments and groundwater. Among them, the process of Mode I can be summed up as “self-gravity action - tensile cracks - surface water scouring - earth fissures”. The process of Mode II is “primary join - surface water infiltration - piping - cave in - earth fissures”. The process of Mode III is “groundwater extraction - aquifer compression - inhomogeneous ground subsidence - earth fissures”. These formation mechanisms of paleochannel-induced earth fissures can be used to predict the fine distribution of shallow buried paleochannels and the overall migration process of the rivers. Thus, this kind of earth fissures is of great significance for understanding the underground paleogeomorphology (buried paleochannel) of the North China Plain and other alluvial plains of the world.

Shaking table tests on braced reinforced concrete frame structure across the earth fissure under earthquake

SummaryA series of shaking table tests on a scaled model were conducted to investigate the effect of steel braces on reinforced concrete frame structure across earth fissure under earthquake. In the test, a 1/15 scaled model structure taking into account soil–structure interaction was designed on the basis of similarity theorem. Seismic response data, including acceleration responses, displacement responses, shear force distributions, and strain amplitudes of column reinforcement were obtained and analyzed by comparing the results of unbraced and braced structure. Results show that with the peak ground acceleration of input motions increased, maximum of inter‐story drifts, shear forces, and strain amplitudes increased, whereas the acceleration amplification factors decreased. Steel braces could obviously reduce the seismic response of the structure, indicating that this retrofit method is an effective control measure for structures across the earth fissure under earthquake. These results are significant for studying the effect of earth fissure on seismic responses of structures.

Geomechanical modeling of subsidence related strains causing earth fissures

Geomechanical modeling of subsidence related strains causing earth fissures

Development characteristics and formation analysis of Baixiang earth fissure on North China plain

The Baixiang earth fissure is a typical earth fissure developed on the North China Plain, about 12 km in length, with NE40° trending, distinct linear emergence, and in good agreement with the South Baixiang fault. Its formation was the result of internal tectonic factors and external dynamic factors. The trenching and drilling data show that the strata in the earth fissure development zone have a striking “two-element” structure: the upper thick silty clay formation and the lower thick sand formation, providing the necessary space for the development of an earth fissure. The seismic exploration data show that the width of the developed earth fissure zone is determined by the fault structure buried at a certain depth under the strata and the horizontal stretching of the overburden. Constrained by such geological structure and stratal properties, a series of small “tensile cracks” are developed at different depths in the development zone. They are further affected by phenomena, such as formation compression and collapse, which are caused by groundwater seepage and sediment laden water migration in the lower sand formation under the influences of external factors (such as groundwater withdrawal and man-made concentrated irrigation). These cracks hence cut through to the earth surface and a cascade of cracks in a certain direction form linear surface fissures. This study importantly reveals the correlation mechanism between the various factors of earth fissures and the transformation mechanism of regional tectonic movements from deep to surface.

Development characteristics and mechanisms of the Taigu–Qixian earth fissure group in the Taiyuan basin, China

Since the 1980s, increasing human activity and continuing over-exploitation of groundwater resources have caused the earth fissures in the rift basin in Shanxi, China, to enter an active phase. Buildings along these earth fissures have been seriously damaged. Four massive earth fissures that developed in the Taigu and Qixian areas of the eastern Taiyuan basin endanger the operational safety of the high-speed railway that passes through this region. Using field observations, measurements, and exploration, we determined that the four earth fissures are parallel to each other, have a northeast trend, and are separated by approximately equal distances. The rupture zones of these earth fissures are generally 10–50 m wide and are formed by the main fissures and secondary fissures. The width of the zone affected by the earth fissures is 20–50 m based on deformation and the damage done to buildings. These fissures formed on the Earth’s surface; their hanging walls are lower than their foot walls, forming normal faults; and the ground surface around the fissures exhibits ridges and depressions. The fissures are connected to deep hidden faults. The fault displacement increases with increasing depth, which is characteristic of syn-sedimentary faults. These earth fissures are characterized by vertical displacement, and their average annual activity rate is 1–3 cm. We believe that the formation of this large-scale fissure group may be related to the tectonic structure of the hidden faults in the basin and may also be affected by the continuous regional extensional stress of the basin. The current increased level of activity could be caused by the over-exploitation of groundwater in the area.

Shaking table tests of RC frame structure across the earth fissure under earthquake

SummaryTo investigate the behavior of a reinforced concrete (RC) frame structure across earth fissure under strong earthquake, a series of shaking table tests on a scaled model were designed and conducted. Three earthquake motion records were selected as input excitations, and the Jiangyou motion has a dramatically greater dynamic effect on the structure mainly due to its inherent rich low‐frequency component. The structural acceleration amplification factor gradually decreased as the peak ground acceleration of input motions increased, implying the progressive degradation of the structure stiffness. The results indicated that the earth fissure site has amplification effect on acceleration of the soil, and the displacement response of frame across the earth fissure was different to that of a typical RC frame structure. The ground floor was the most vulnerable story of the RC frame across the earth fissure.