Coseismic Response Research Articles

Co-Seismic Response of Bedrock Temperature to the Ms6.3 Kangding Earthquake on 22 November 2014 in Sichuan, China

In this paper, we report the co-seismic temperature response of the Ms6.3 Kangding earthquake in Sichuan, China, which occurred within a bedrock temperature monitoring station network constructed in the east of the Qinghai-Tibet Plateau. Results indicate that two kinds of co-seismic responses of bedrock temperature, exponential and step-rise ones, were recorded at different stations. As for the former, the amplitude of co-seismic response is about 5.6–11.5 mK (the average value is 7.33 mK), while the latter is about 0.31–0.98 mK (the average value is 0.52 mK). These two kinds of responses would be indicative of the two different mechanisms for change in temperature. On the one hand, the exponential responses represent the effects of fluid advection along the borehole wall, which are associated with a finite quantity of heat produced by earthquake-driven transient fluid flow. The step-rise responses, on the other hand, represent the direct response of temperature to change in the crustal stress accompanying with earthquake. We still tested relationship between stress variation and temperature response on the rock samples taken from the boreholes, and the average value is 0.77 mK/MPa. Upon thus, these step-rise temperature responses imply that co-seismic change in mean stress is about 0.40 MPa. We simplify effects of fluid by presuming a one-dimensional model where the flow is either up or down based on a pressure change due to compression or tension. The stress state, compression or tension, deduced by the direction of the fluid flow is qualitatively accordant with the direct response of bedrock temperature to stress change. In summary, characteristic changes in bedrock temperature occurred coincidentally with the earthquake at different stations, agreeing generally with regional stress adjustments accompanying the earthquake. Changes in bedrock temperature do seem to offer a useful means of monitoring dynamic changes in shallow crustal stress.

岷县6.6级地震震前异常及其水位水温同震响应讨论

分析了2013年7月22日甘肃岷县6.6级地震前甘肃地区的水位、流量和水温资料的变化情况，结果发现在这次地震前两个测点的资料存在明显的震前异常，其中清水李沟流量为中长期异常，清水温泉水温为短临异常。另外部分水位、流量和水温测点的资料记录到不同程度的同震效应，形态有突升、突降和缓变型等，持续时间不等，其中数字化水位、水温均在地震后10分钟至数小时之内恢复，而传统的人工流量观测持续1到2个月。记录同震响应的测点与震中位置、方向、距离无明显规律。 The variations of water level, flow and temperature data collected in Gansu area before the 6.6-magnitude earthquake of Min County on July 22th 2013 were analyzed. Two points showed evident abnormities just before this earthquake. The flow discharges of Ligou and Qingshui showed medium or long-term anomaly, while the temperature of thermal spring in Qingshui showed short-impending anomaly. Besides, the water level, flow and temperature in some stations recorded a different degree of coseismic response. The configurations of these responses included sudden rise, sudden drop and slow-change type. The duration of these responses varied. Digital-observed water level and temperature recovered in a time from 10 minutes to several hours after the earthquake, while the traditional man-observed flow lasted 1 to 2 months. The observation stations that had co-seism responses showed no obvious regularity with epicenter location, direction or distance.

Quantitative Assessment of the Mechanisms of Earthquake-Induced Groundwater-Level Change in the MP Well, Three Gorges Area

Earthquake-induced groundwater-level changes have been widely studied, though the mechanisms causing coseismic responses are still debated. In this study, we employ several models to fit the coseismic groundwater-level changes caused by the 2008 Wenchuan earthquake in the MP well, located in the Three Gorges Dam. The fits for all models are about the same. By comparing the model results with the results from tidal response and baseflow recession analyses, we conclude that a transient permeability model can best describe the coseismic groundwater-level changes in the MP well. The discharge from the Changmutuo fault zone estimated from the one-dimensional groundwater flow model during the 20 days following the earthquake is about 310 ± 90 m3.

Co-seismic multilayer water temperature and water level changes associated with Wenchuan and Tohoku-Oki earthquakes in the Chuan no. 03 well, China

The present paper shows analysis of water level (the distance from the land surface to the water in the well under static condition) and water temperature observed at three different levels of Chuan no. 03 well to study the changes associated with the Wenchuan earthquake of 2008 and the 2011 Tohoku-Oki earthquake. Our analysis shows co-seismic changes in water level and water temperature associated with the increase in compressive stress associated with the Wenchuan earthquake. The water level shows an increase, whereas there was drop in water temperature at the shallow depth (395 m) and enhancement of water temperature at the middle (595 m) and the bottom (765 m) layers. However, no step change in water level or temperature of Chuan no. 03 well is observed associated with the Tohoku-Oki earthquake, only seismic wave propagation-induced water level oscillation and led to co-seismic response of water temperature. The analysis of the co-seismic responses and post-earthquake adjustment processes combined with the borehole histogram and the borehole temperature gradient data clearly show co-seismic changes in water temperature that could be closely associated with the changes in the regional stress and strain state and the distribution of the aquifer and the characteristics of the aquifer. The observed temperature variation of different layers in the borehole is likely to be controlled by the flow of water in the horizontal direction.

Co-seismic response of water level in the Jingle well (China) associated with the Gorkha Nepal (Mw 7.8) earthquake

Changes in co-seismic water levels associated with the Gorkha Nepal earthquake (25 April 2015, Mw 7.8) were recorded in the Jingle well in Shanxi Province China (longitude E112.03°, latitude N38.35°, about 2769km from epicenter). Based on the observed water levels, we clearly identified signals relating to P, S and surface waves. However, the water temperature recorded at a depth of 350m shows no co-seismic changes. A spectrum analysis of co-seismic variations of water level shows that the oscillation frequency and amplitude of water level in the borehole are determined by the natural frequency of the borehole, which is not associated with the propagation of seismic waves. The borehole-aquifer system shows a large amplification associated with ground vibrations generated by earthquakes. Considering the local hydro-geological map and the temperature gradient of the Jingle well, a large volume “groundwater reservoir” model can be used to explain these processes. Due to seismic wave propagation, the volume of a well-confined aquifer expands and contracts forming fractures that change the water flow. In the well-confined aquifer, water levels oscillate simultaneously with high amplitude ground shaking during earthquakes. However, the water in the center of the “underground reservoir” remains relatively stationary, without any changes in the water temperature. In addition, a possible precursor wave is recorded in the water level at the Jingle well prior to the Gorkha earthquake.

岳庄深井水位监测数据统计与地震同震响应特征分析

地震会造成震源周围地质结构的应力状态变化，导致含水层的受力状态相应改变，因而深井的水位也会出现同步变化。本文针对山东省邹城市的特殊地质结构，以该市岳庄深井所记录的水位监测数据统计结果为基础，进行了地震同震响应特征分析。结果表明，该深井的水位变化对ML 4.0震级以上地震呈现良好的同震响应特征；记录的地震同震响应特征可分为五种类型，其中阶梯型和振荡型出现频次较高，是主要的两种类型。因此，利用该深井的水位监测统计数据进行地震的同震响应特征分析和开展地震监测是一种可行的方法。 The earthquake can change stress state around geological structure so as to cause stress change in the aquifer layer and a synchronous change of the deep well water level. This paper dealt with the seismic response characteristic based on the special geological structure of Zoucheng City in Shandong Province and the water level monitoring statistical data of the Yue Zhuang deep well. The research results showed that this deep well had a good response ability to the seismic above ML4.0 level. The recorded coseismic response characteristics can be divided into five kinds in which the ladder and the wave modes are occurred in higher frequency. Therefore the water level monitoring statistical data and seismic response characteristic of the deep well can be used to provide a good way for earthquake monitoring.

Coseismic response of water level in Changping well, China, to the Mw 9.0 Tohoku earthquake

Summary A water-level meter installed in Changping well, China, recorded coseismic fluctuations and a step change induced by the M w 9.0 Tohoku earthquake of 11 March 2011. Here we analyse the correlation between water level in the well and vertical ground motions recorded at a nearby surface site, and we examine the relationship between the characteristics of these two datasets and the well-aquifer system parameters. During the arrival period of P- and S-waves, the water level provides information about the intensification of high-frequency ground motions. During the arrival period of the surface waves, the amplitude of water-level fluctuations was closely related to the velocity of vertical-component surface motions. The fluctuation periods of these two parameters are in the range 15–35 s, and the period of oscillation displays a large-to-small characteristic behaviour. The amplification effect on the water level in Changping well, driven by the pressure fluctuation induced by the surface wave, was relatively small, but a low-to-high characteristic is apparent during the coseismic period, related to the gradual enhancement of aquifer permeability due to the action of seismic waves. The coseismic step increase in water level was related to the enhancement of aquifer permeability under the action of seismic waves, and the results of an inversion of water-level tidal-response characteristics show that permeability increased by ∼6.56 × 10 −14 m 2 in the vicinity of Changping well in response to the action of seismic waves emanating from the Tohoku earthquake.

Co-seismic changes of well water level and volume strain meter in capital area and its vicinity, due to the Nov.14, 2001 Ms8.1 Kunlun Mountain earthquake, China

The Kunlunshan Mountain Ms8.1 earthquake, occurred in Nov.14, 2001, is the first event with magnitude more than 8 in the China earthquake monitoring history, specifically at the beginning of digital techniques in precursor monitoring networks. Any investigation of recorded data on this earthquake is very important for testing the operation of the digital monitoring networks and understanding the preparation, occurrence, and adjustment of stress/strain of strong continental earthquakes. In this paper we investigated the co-seismic response changes of well water level of groundwater and volume strain meter of bore hole in digital earthquake monitoring network of Capital area and its vicinity, due to the Nov.14, 2001 Ms8.1 Kunlun Mountain earthquake. The responding time, shapes or manners, amplitudes, and lasting time of well water level and strain-meters to seismic wave are studied in comparison. Then we discussed the possibility that the response changes of groundwater to strong distant earthquakes can be understood as one kind of observing evidence of stress/strain changes induced by distant earthquake.

Parallel numerical analysis of the failure characteristics of earthquake-induced landslides

Earthquake-induced landslides are serious natural hazards that shocked us with tremendous casualties and great economic losses in many mountainous areas around the world. However, predicting and preventing the earthquake-induced landslides is very difficult due to the complicated relationship between seismic dynamics and coseismic landsliding. Comprehensive understanding of earthquake-induced landslides from the perspective of seismic dynamic mechanism remains inadequate at present. This study employs an elastoplastic spectral element method incorporating parallel computing and represents a realistic three-dimensional slope model via a semi-structured hexahedral mesh to investigate the dynamic failure characteristics of earthquake-induced landslides. Dynamic behaviours of slopes are simulated using a continuumbased approach with a Mohr-Coulomb yield criterion. Displacement fields are calculated using the shear strength reduction technique. Pseudo-static seismic loading is performed to assess the slope stability quantitatively and complex topography is taken into consideration. The Xinzhong landslide that occurred in Beichuan Country is one of destructively collapsing landslides triggered by the Wenchuan earthquake and is therefore selected as a case study for discussion. Three-dimensional visualization of the calculated results quantitatively demonstrated that the three-dimensional numerical model well reproduced the coseismic landsliding response and its essential dynamic failure pattern, which could not be purely captured by Geographic Information Systems (GIS) and Remote Sensing (RS) technologies and calculated using simply two-dimensional numerical model. The numerical results also showed that tensile and shear fractures had significant influences on the nature of the failed surface development. In addition, the presence of seismic loading in the slope could cause obvious disturbances for the slope stability. Comparative analysis indicated that the shear surface of the earthquake-induced slope was shorter and the tension crack surface was deeper than that of the normal gravity condition. Moreover, the landslide mainly occurred in the transition from the upper to lower part of the slope, indicating that the slope topography was one of the crucial factors resulting in slope failure. Although the model was constructed without the presence of a pre-existing failure surface, comparative analysis addressed that the failure surface obtained by the numerical simulation was in close agreement with that by the post-failure investigations. The results could provide insight into better understanding of the relationship between landslide and seismic dynamic mechanism. The study has practical significance for the effective prevention and mitigation of earthquake-induced landslide hazards.

What 2‐D multichannel seismic and multibeam bathymetric data tell us about the North Sumatra wedge structure and coseismic response

AbstractRecent large earthquakes have prompted studies to reevaluate seismicity and rupture propagation behavior along the world's major subduction margins. Our study area covers the entire fore arc from northwest of northern Sumatra to west of Simeulue Island, the southern portion of the 2004 tsunamigenic earthquake rupture zone. The accretionary prism width is up to ~180 km, water depths between ~4.5 km near the Sunda Trench and <1 km on fore‐arc high. The wedge consists of a steep outer slope (5–12°), a plateau ~100–120 km wide with anticlinal folds spaced 2–15 km apart, and a steep inner slope adjacent to the Aceh Basin. Analysis of seismic profiles and bathymetry reveal three main structural zones consistent along‐strike, from the trench landward: (1) predominantly landward vergent folds, (2) mixed vergent folds, and (3) predominantly seaward vergent folds. This paper uses those zones to propose a geometry of an underlying rigid backstop. This backstop is seaward dipping and extends from under the Aceh Basin to beneath the mixed vergence zone. A dynamic backstop possibly exists seaward of the rigid backstop and is responsible for the steep slope of the outer prism. Indurated accreted sediments form the landward vergence zone. Along with the possible dynamic backstop beneath the outer wedge, and the rigid backstop in the inner wedge, all behave as a solid block coseismically. This block allows great earthquake rupture to propagate farther seaward toward the Sunda Trench, with resultant hazardous tsunamigenic potential.

Mechanism of co-seismic water level change following four great earthquakes – insights from co-seismic responses throughout the Chinese mainland

We analyze the co-seismic groundwater level responses to four great earthquakes recorded by China's network of groundwater monitoring wells. The large number of operational wells (164 wells for the 2007 Mw 8.5 Sumatra earthquake, 245 wells for the Mw 7.9 Wenchuan earthquake, 228 wells for the Mw 9.0 Tohoku earthquake and 223 wells for 2012 Mw 8.6 Sumatra earthquake) and co-seismic responses provide an opportunity to test hypotheses on mechanisms for co-seismic water level changes. Overall, the co-seismic water level responses are complex over large spatial scales, and there is great variability both in the sign and amplitude of water level responses in the data set. As shown in previous studies, permeability change, rather than static strain, is a more plausible mechanism to explain most of the co-seismic responses. However, we find through tidal analysis of water level responses to solid Earth tide that only one third of these wells that showed a sustained post-seismic response can be explained by earthquake-induced permeability change in aquifers, and these wells had sustained (>30 days) water level changes. Wells that did not show sustained changes are more likely affected by permeability changes only immediately adjacent to the wellbore.

Analysis of the Far-Field Co-seismic and Post-seismic Responses Caused by the 2011 M W 9.0 Tohoku-Oki Earthquake

We analyzed the far-field co-seismic response of the M W 9.0 Tohoku-Oki earthquake, which occurred on March 11th 2011 at the Japan Trench plate boundary. Our analysis indicates that the far-field co-seismic displacement was very sensitive to the magnitude of this event, and that a significant co-seismic surface displacement from earthquakes in the Japan Trench region can be observed in Eurasia only for events of M W ≥ 8.0. We also analyzed the temporal characteristics of the near-field post-seismic deformation caused by the afterslip and the viscoelastic relaxation following the Japan earthquake. Next, we performed a simulation to analyze the influence of the two post-seismic effects previously mentioned on the far-field post-seismic crustal deformation. The simulation results help explain the post-seismic crustal deformation observed on the Chinese mainland 1.5 years after the event. Fitting results revealed that after the M W 9.0 Tohoku-Oki earthquake, the afterslip decayed exponentially, and may eventually disappear after 4 years. The far-field post-seismic displacement in Eurasia caused by the viscoelastic relaxation following this earthquake will reach the same magnitude as the co-seismic displacement in approximately 10 years. In addition, the co- and post-seismic Coulomb stress on several NE-trending faults in the northeastern and northern regions of the Chinese mainland were significantly enhanced because of the M W 9.0 earthquake, especially on the Yilan-Yitong and the Dunhua-Mishan faults (the northern section of the Tan-Lu fault zone) as well as the Yalujiang and the Fuyu-Zhaodong faults.

A new capacitive borehole tiltmeter for crustal deformation measurement and its performance analysis

Borehole inclinometers are important observation instruments used to measure ground tilt movement and monitor crustal deformation of solid tides and geological landslide disasters. They are widely used in oil exploration, mineral resource drilling, well logging, exploration and other fields. There is potential for development of rock stress strain monitoring tools. Many types of tiltmeters have been installed, such as SQ-7, FSQ, VS and JB. However, these tiltmeters are generally installed in a deep cave to avoid the interference of temperature, humidity, and human activities. With the urbanization of human society, suitable installation locations are difficult to find. To solve the problem, a two-component borehole tiltmeter, named the CBT-type tiltmeter, is proposed in this paper. It can be installed in a borehole less than 500m deep to eliminate environmental influences. The tiltmeter is composed of two sophisticated gravitational swing and two capacitive transducers. From preliminary theory and experiment analysis, its linear correlation coefficient is higher than 0.99, its co-seismic response is rapid and its noise level is up to 10−4 arc seconds in practice.

Coseismic and postseismic motion of a landslide: Observations, modeling, and analogy with tectonic faults

AbstractWe document the first time series of a landslide reactivation by an earthquake using continuous GPS measurements over the Maca landslide (Peru). Our survey shows a coseismic response of the landslide of about 2 cm, followed by a relaxation period of 5 weeks during which postseismic slip is 3 times greater than the coseismic displacement itself. Our results confirm the coseismic activation of landslides and provide the first observation of a postseismic displacement. These observations are consistent with a mechanical model where slip on the landslide basal interface is governed by rate and state friction, analogous to the mechanics of creeping tectonic faults, opening new perspectives to study the mechanics of landslides and active faults.

Delineation and interpretation of spatial coseismic response of groundwater levels in shallow and deep parts of an alluvial plain to different earthquakes: A case study of the Kumamoto City area, southwest Japan

Coseismic changes in groundwater levels have been investigated throughout the world, but most studies have focused on the effects of one large earthquake. The aim of this study was to elucidate the spatial patterns of level changes in response to several earthquakes, and the relationship of the patterns to shallow and deep groundwater in the same area. We selected the Kumamoto City area in southwest Japan, a region with one of the richest groundwater resources in Japan, as our study site. Data from hourly measurements of groundwater levels in 54 wells were used to characterize the coseismic responses to four earthquakes that occurred in 2000, 2001, 2005, and 2008. Although the distance to the hypocenter (12–2573km), and seismic energy (Mw=5.0–8.0) of these earthquakes varied, systematic groundwater level changes were observed in the range of 0.01–0.67m. Spatial patters of the level changes were clarified by interpolating the point data by a spline method. The zones where coseismic rises were observed were generally wider for deep groundwater than for shallow groundwater, probably as a result of an increase in compressive stress. General trends in the changes in groundwater levels, and calculated pressure changes, were clarified to be consistent in the deep groundwater, but the coseismic increases or decreases in compressive stress in the shallow groundwater were variable, depending on the distance to the earthquake epicenter. We developed a conceptual model of the mechanism underlying this phenomenon by assuming permeability enhancement induced by elastic strain and pore-pressure change over the depth range. In addition, the importance of local geology was identified, because levels in the area of Togawa lava (a porous andesite) tended to change more in magnitude, and more quickly, with a shorter recovery time, than levels measured in the area outside the lava.

Tidal response variation and recovery following the Wenchuan earthquake from water level data of multiple wells in the nearfield

Tidal response variation and recovery following the Wenchuan earthquake from water level data of multiple wells in the nearfield

Coseismic response of groundwater level in the Three Gorges well network and its relationship to aquifer parameters

The 12 May 2008 Ms 8.0 Wenchuan earthquake caused notable changes in the water levels of wells in the Three Gorges area. This work examines the relationship between these coseismic changes in water level and the changes in aquifer parameters. Three wells in the area with good responses to earth tide were chosen for analysis. Water-level data from February to June 2008 were used to calculate the aquifer transmissivity, permeability and specific storage of the rocks, and analyze the relationship between the coseismic responses of the wells and their aquifer parameters. The results show that the Wenchuan earthquake changed these parameters considerably, thereby controlling co- and postseismic variations of water level. The values of these parameters prior to the earthquake are linearly related with the amplitudes of coseismic variations in water level. The larger the aquifer transmissivity, the more remarkable the coseismic change in water level. During the earthquake, changes in aquifer parameters were found to be associated with coseismic variations in water level, with the larger changes occurring when the coseismic variation in water level was larger. The tectonic setting has a certain degree of influence on the co- and postseismic changes in water level. The permeability structures of the fault zone appear to determine the manner of coseismic variation in water level. Moreover, it seems that the water level in wells where groundwater converges more easily can recover faster following an earthquake. Insight from this study helps to improve understanding of the characteristics of water-level changes caused by earthquakes.

1954年山丹7 1/4 级地震的孕震构造和发震机制探讨

Located in the front margin of the northeastern Tibetan Plateau, the Longshoushan fault zone is one of the boundary faults between the Hexi corridor and the Alxa block. Although the resolution of observation is limited, the 1954 M7(1/4) earthquake on the Longshoushan fault zone is a rare big event in this zone with modern seismological observation and documentation. During this earthquake, one continuous dextral-normal rupture occurred with a length of only 7 km along a transfer fault connecting two secondary faults of the Longshoushan fault zone. However, the dextral-normal sense of this surface rupture is contrary to the tectonic kinematics in this area. Based on recent field investigation and mapping, two phenomena were discovered. Firstly, except the one appeared on the transform fault, no surface rupture zone is found on the branches of the Longshoushn fault zone. Secondly, the main damage caused by earthquake is distributed on the region between the northern and the southern branches of the Longshoushan fault zone. These two findings indicate that the 1954 earthquake was caused by the main faults rather than the transfer fault of the Longshoushan fault zone, and the co-seismic surface rupture on the transfer fault is only a form of stress release at local portion. According to calculation of static co-seismic Coulomb stress change, the surface rupture could be triggered by an earthquake on the southern branch of the Longshoushan fault zone. Furthermore, in consideration of the possibility of dynamic triggering along the northern branch of the Longshoushan fault zone, the surface rupture should be the co-seismic response to the earthquake occurred on the main branches of the Longshoushan fault zone. Relocation of the small earthquakes also shows that a narrow inverted north-extending triangle about 10 km wide was formed between the northern and the southern faults of the Longshoushan fault zone.

Changes in groundwater level and temperature induced by distant earthquakes

We analyzed the co-seismic responses of groundwater level and temperature in the Tayuan Well, Beijing, China, induced by 85 distant earthquakes over the period from January 2004 to July 2009. The results show that the Tayuan Well records earthquakes worldwide and that the co-seismic response shows the following pattern: water-level oscillation, temperature decrease, oscillations stop, return to normal temperature. The amplitudes of changes in water level and temperature are related to the earthquake magnitude and the distance to the epicenter. We discuss the mechanisms of the decrease in water temperature during the period of oscillations in water level, and the mechanisms of the temperature increase subsequent to the cessation of oscillations. We also analyze the results of previous studies on co-seismic response mechanisms, and consider the mechanisms of gas escape, heat diffusion, and cold-water seepage. These mechanisms may have induced the decrease in water temperature recorded in the present study, and the subsequent return to normal temperatures was due to heat exchange between the well water and the surrounding wall rock.

Temperature changes in the KUN-1 borehole, Kunashir Island, induced by the Tohoku Earthquake (March 11, 2011, M = 9.0)

The results of continuous (September 2010–September 2011) temperature monitoring in the 300-m-deep borehole on Kunashir Island are presented. There were several earthquakes, including the Tohoku one (March 3, 2012, M = 9.0), during the observation period, and they produced a significant coseismic response in the temperature field. The Tohoku earthquake was preceded by a constant decrease in temperature at the depth of 240 m with a mean rate of 0.02 K per month. The coseismic response was manifested in an abrupt (in a day) growth of temperature by 1.2 K. The relationships between the earthquake characteristics (magnitude, epicentral distance) and the amplitude of the coseismic temperature response in the borehole have been estimated. The deformation mechanism of the temperature response to earthquake preparation and implementation processes is suggested.