Bedrock Level Research Articles

Probabilistic Assessment of Seismic Hazard for Uttarakhand State of India

Abstract Uttarakhand state of India, being located in the seismically active Himalayan mountain range, is highly prone to seismic hazards. This study presents assessment of seismic hazard of Uttarakhand through probabilistic approach. For conducting this study, a homogenous earthquake catalogue for moment magnitude during the period 1953 - 2020 with magnitude range of 2.0 - 6.9 consisting of 522 events was used. Various geological structures viz. folds, faults and lineament as well as thrust, have been identified in the associated regions. The state was divided into several grid points and the seismic hazard was evaluated for each of the grid points through probabilistic method. Finally, based on the analysis results, bedrock level hazard maps were developed for the state for contingency level earthquake (CLE) and maximum credible earthquake (MCE). The estimated peak ground acceleration (PGA) of the state is in the range of 0.16g-0.52g for CLE and the PGA varies for 0.20g-0.61g for MCE level earthquake. Main Central Thrust (MCT), Sunder Nagar fault and Ropar fault were observed to be more hazardous in the northern region of the state.

Seismic hazard assessment and site-specific response spectrum at bed rock level for Ongole city, India: a deterministic framework

Seismic hazard assessment and site-specific response spectrum at bed rock level for Ongole city, India: a deterministic framework

Deterministic Seismic Hazard Map Using Region-Specific GMPEs of Maharashtra State, India

Maharashtra stands out as a crucial state in India, demonstrating significant progress in infrastructural development and industrialization. Several prominent cities, including Mumbai, Pune, Nagpur, etc., are significantly contributing to the Indian economy. Considering the importance of the state, a deterministic seismic hazard analysis is executed to reduce the damages to critical and important structures and fatalities caused due to earthquakes. Past earthquakes data are collected within and around the state to prepare a homogenised earthquake catalogue. Seven seismic zones are prepared using K- mean cluster analysis. Independent earthquake events i.e., mainshocks are identified using four renowned declustering methods. Additionally, with the help of mainshocks from each zone, the maximum observed earthquake magnitude ( m^max) and positive correction factor (Δ) are estimated. By superimposing all the mainshocks (after adding Δ) onto the fault map, the maximum observed possible earthquake magnitude of all faults ( M^max) are assigned to each fault. M^max value is used to estimate surface rupture length (RLD) and consecutively, the maximum magnitude (MMax) from fault sources are estimated. Three region-specific ground motion prediction equations (GMPEs) are adopted in the logic trees assigning a proper weightage to each GMPE. A seismic hazard contour maps are prepared at bedrock level, C, and D-type soil sites for Maharashtra. In the western part of the study area, the maximum PGA value is found to be 0.58 g, 0.70 g, and 0.33 g at bedrock level, C, and D-type sites, respectively.

A novel joint for driven concrete geothermal energy pile foundations

Geothermal energy pile foundations are among the most common types of energy geostructures which provide both structural support and can be used as a source with ground source heat pumps for heating and cooling buildings. Energy piles can be categorized into cast-in-place and precast piles. Driven precast concrete energy piles can be installed up to the bedrock level, with higher quality, lower cost, and faster installation process, compared to cast-in-place energy piles. Precast concrete driven energy pile foundations have not been commonly utilised due to existing problems with a suitable type of joint that could connect precast segments and allow continuity of heat exchanging pipes. An innovative and novel steel driven energy pile (DEP) joint is presented in this paper which can provide structural integrity between the segments and leak-proof coupling between the heat exchanging pipes. Both sizes of DEP joints passed 1000 impact blows of 28 MPa, they remained undamaged during the bending tests with a flexural stiffness of 3500 kN.m2, and 7720 kN.m2 for the 267 mm and 350 mm joints, respectively. Additionally, the pipes used in the prototype joints and piles indicated no leakage or pressure drop in the hydraulic pressure tests subjected to 690 kPa pressure.

Development of Synthetic Ground Motion-based Attenuation Relationship for Bihar Region for Seismic Ground Response Analysis Considering Central Seismic Gap

Ground Motion Prediction Equation (GMPE) is one of the significantly important tools to perform the seismic hazards analysis of any region. Therefore, the development of GMPEs at the bedrock level is utmost important especially when the region does not have any earthquake recording stations. The present study discussed the development of a GMPE at bedrock level for the Bihar region based on the stochastic model. The different seismic parameters such as magnitudes (Mw) 4.0‐8.5, spectral periods of 0‐10 s and distances up to 300 km have been considered for the stochastic model. Based on the results, it was found that the stochastic model is capable to predict the ground motion synthetically and the proposed GMPE, for Bihar region, predicts the spectral acceleration in most precise way. Further, the ground motion amplification analysis was carried out using synthetically generated bedrock motion to analyze the effect of soil deposits on the amplification or de‐amplification of the bedrock peak ground acceleration. It was found that that the seismic wave gets amplified at ground level by 10% to 70% from the input motion PGA ranging from 0.175g‐0.435g, indicating amplification and de‐amplification of seismic wave. The maximum spectral acceleration at surface level was also found to be increased by approximately 60%, 56% and 27%, when bedrock input motion of PGA = 0.175g, 0.256g and 0.435g, respectively. Thus, based on the results, it can be stated that the developed GMPE can be used to assess the seismic hazards analysis in Bihar region. Further, it can be suggested that there is a need of the development of a predictive attenuation relationship at the surface level PGA, for Bihar region or any earthquake prone area, incorporating different site classes and regional seismicity since, the seismic wave amplified due to the presence of soil deposits.

Ataköy Gözlem Kuyusunda Saha Tepki Tahminleri

Site response analyses are seen to be the reliable way of reproducing and predicting earthquake input motions. The analyses are generally performed by adopting equivalent linear or nonlinear approaches solving the problem in time or frequency domains. Instrumented geotechnical downhole arrays, in this regard, are very important as to obtaining earthquake data through the soil deposits. This data can eventually be used to verify the approaches developed for site response analyses. In this study, the input motions of the 24.05.2014 (Aegean) earthquake event recorded at relatively recently installed Atakoy geotechnical downhole array are assessed. Moreover, the recorded input motions at the bottom bedrock level of the downhole array are simulated in the East-West and North-South directions. The site response analyses are conducted based on frequency domain equivalent linear approach. The peak ground acceleration and the spectral accelerations of the predicted input motions are compared with the recorded ones at 70 m, 50 m, 25 m and at the ground surface. The results indicate that the spectral acceleration predictions can be simulated well until the depth of 50 m. At 25 m and at ground surface, the predictions are always greater than the recorded one. However, the predictions still exhibits good indication of actual values in the North-South direction. In terms of peak ground acceleration and shear strain profiles, the predictions display the soil layers featured with different soil properties. The equivalent linear approach appears to be suited reasonably well in site response analysis.

Improved intensity measures considering soil inelastic properties via multi-regression analysis

At certain depths, the elastic properties of the ground are not affected by seismic waves. However, as they reach the surface, the soil density decreases and so does its elastic limit. This means that the expected ground motion acting at the foundation of a structure cannot be adequately described without considering the inelastic response of the soil near the surface. Therefore, one of the key elements in characterizing the seismic response of civil structures is the site effect. These depend mainly on the parameters of the soil beneath the structure and the features of the ground motion acting at the depth, where non-linear effects are negligible. Therefore, the main objective of this paper is to find an intensity measure that incorporates the information provided by the soil profile under the structure and the ground motion acting at the bedrock level. Due to the random nature of both elements, a probabilistic framework using Monte Carlo simulation has been developed to analyze this problem. For this purpose, random soil profiles have been generated to obtain a representative sample of likely scenarios of the study area. A large database of Colombian ground motion records has been used to model the seismic hazard. Finally, power functions capable of relating the input variables to the dynamic response of a large set of reinforced concrete structures have been derived by considering multi-regression analysis. It has been observed that, in several cases, intensity measures extracted from the displacement spectrum appear in the mathematical arrangements. These functions could be used to improve the efficiency of seismic risk prediction at the urban level.

Quantitative strong motion simulations at three locations in downtown Mashiki during the 2016 Kumamoto Earthquake (Mw 7.0) based on the nonlinear ground response analyses with soil liquefaction

The mainshock of the 2016 Kumamoto Earthquake (Mw 7.0) caused extensive damage to buildings in downtown Mashiki, Kumamoto Prefecture, Japan. The heavy building damage in the area was associated with both strong ground motion and building response characteristics. Fortunately, there were two strong motion stations in the area and the observed records during the mainshock were distributed, showing peak ground velocities exceeding 100 cm/s on the surface. The level of shaking would be sufficient to make soft surface sediments nonlinear. To reproduce observed ground motions quantitatively, one-dimensional nonlinear effective-stress time-history analyses were conducted at three locations in downtown Mashiki. The input wave was employed as either the observed underground wave or simulated outcrop input motion based on the diffuse field theory. The main purpose of the study was twofold: to investigate the proper soil constitutive relationship and its nonlinear parameters based on the limited amount of in situ information, and to validate the method of input motion evaluation at the seismological bedrock level based on diffuse field theory. The nonlinear time history analyses using the on-site boring survey and the outcrop wave based on diffuse field theory showed that the waveform of the mainshock observed on the ground surface was explained with sufficient accuracy. In addition, the results of the effective stress analysis indicated that soil liquefaction might have occurred in the area with thick surface layers along the Akitsu River where the water table was considered to be quite shallow.Graphical

Ultrahigh-resolution shear-wave reflection imaging of vertical-component data in a quick-clay prone to landslide area in southwest Sweden

We have investigated the potential of ultrahigh-resolution seismic reflection imaging of vertical-component data to identify hazardous conditions in a quick-clay landslide area in southwest Sweden. A high-fold survey with a fine shot and receiver spacing has been acquired using a 5 kg sledgehammer, vertical hit, with the objective of producing a high-quality unaliased shear-wave reflection section retrieved from vertical-component data. On the receiver side, 1C wireless recorders are deployed in a fixed geometry juxtaposed to a landstreamer of 3C-microelectro mechanical system (MEMS)-based units, which recorded in a roll strategy to cover most of the profile length. Particle motion analysis of main reflections has been conducted on the 3C MEMS sensors, given their side-by-side location with the wireless recorders, to inspect the wave polarization. Distinct shear-wave reflections in an extremely slow shear velocity medium (70–100 m/s) imply a vertical super resolution of 1–2 m down to a bedrock level of 40 m deep. Interestingly and as shown in earlier studies, quick clays appear to overlie the coarse-grained horizons justifying why their high-resolution imaging can be significant for quick-clay landslide studies and a better understanding of potential risks. Two shallow reflections are delineated through a combination of first-break traveltime tomography for P and S waves and reflection seismic processing for P- and S-reflections of the vertical-component data. After seismic imaging and borehole data correlation, the shallowest reflection is interpreted to be from coarse-grained materials interbedded within normally consolidated clays and the deepest one from an undulating bedrock. Interpretations of the S-S processing outcomes indicate that the coarse-grained layers are not homogeneous because of the generation of strong shear-wave diffractions, suggesting the presence of either large boulders or patchy sandy-silty conditions.

A suite of broadband physics‐based ground motion simulations for the Istanbul region

AbstractPhysics‐based earthquake ground motion simulations (GMS) have acquired significant growth over the last two decades, mainly due to the explosive developments of high‐performance computing techniques and resources. These techniques benefit high/medium seismicity regions such as the city of Istanbul, which presents insufficient historical ground motion data to properly estimate seismic hazard and risk. We circumvent this reality with the aid of the Texas Advanced Computing Center (TACC) facilities to perform a suite of 57 high‐fidelity broadband (8–12 Hz) large‐scale physics‐based GMS for a region in Istanbul, Turkey. This paper focuses on the details of simulated GMS: (i) validation of the GMS approach against recorded ground motions produced by the 2019 Silivri earthquake; (ii) characteristics of 57 different source models, which aim to consider the uncertainties of many fault rupture features, including the length and width, dip, strike, and rake angles of considered fault planes, as well as hypocenter locations and earthquake magnitudes ranging between 6.5 and 7.2; (iii) high‐resolution topography and bathymetry and seismic data that are incorporated into all GMS; (iv) simulation results, such as PGAs and PGVs versus and distances to fault ruptures (), of 2912 surface stations for all 57 GMS. More importantly, this research provides a massive database of displacement, velocity and acceleration time histories in all three directions over more than 20,000 stations at both surface and bedrock levels. Such site‐specific high‐density and ‐frequency simulated ground motions can notably contribute to the seismic risk assessment of this region and many other applications.

Linear equivalent seismic response of a surface foundation excited by an SH harmonic wave

The main objective of this study is to analyse the effect of the non-linear behaviour of the soil on the seismic response of a foundation by taking into account the soil-structure interaction. The foundation is square-shaped, and rigid, resting on the surface of a homogeneous semi-infinite soil, and solicited only by the incident harmonic wave SH. However, for higher deformations (during strong earthquakes), the behaviour of the soil will be characterised by a nonlinear behaviour law. The phenomenon of soil nonlinearity due to the seismic excitation imposed on the soil is reflected in the curve of reduction of the normalised shear modulus G/G max and the curve of increase of the normalised hysteretic damping coefficient ξ/ξ max as a function of the unit shear deformation γ/γr. This behaviour is obtained by the equivalent linear method with the Masing model implemented in the one-dimensional (1D) computational code Caldynasoil. In this study, first, determine the nonlinear behaviour of a soil profile stressed by different levels of seismic accelerations applied at the bedrock level. The Caldynasoil computational code was used to find the variations of the nonlinear dynamic properties of the soil profile for different levels of seismic loading. Secondly, integrating the nonlinear dimensionless properties of the soil in a three-dimensional computational code Fonvib_Wave based on the boundary elements method combined with the theory of thin layers (BEM-TLM) in the frequency domain allows calculating the nonlinear displacements of a surface foundation. The obtained results represent the influence of the nonlinear behaviour of the soil on the vibration modes of a rigid foundation subjected to a shear wave SH as a function of the dimensionless frequency a0, and the angles of incidence θV and θH. The conclusions that may predict from this research have shown the importance of the influence of the nonlinear behaviour of the soil and the angles of incidence of the SH wave on the response of the soil-foundation system compared to the linear case.

A Simplified Approach for Analysis of MDOF Systems Considering Soil - Structure Coupling

It is common to design structures on the fundamental assumption that the base is fixed and that the ground motion experienced by its base is the same as the free-field ground motion. For structures supported on soft soil, the base motion experienced by the structure is generally different from the free-field motion, as it could include possible sliding and rocking motion of the flexible medium and dissipation of vibration energy through the soil in the form of damping. The seismic response of a structure at a particular location depends on the characteristics of ground motion at source, and; modified mode shapes and vibration periods because of soil structure coupling. Thus, the ground motion that reaches the foundation can be significantly different from that at bedrock level and there is a possibility of response amplification when vibration period of the structure is close to that of the input ground motion modified by local soil conditions. Soil Structure Coupling (SSC) is a process wherein the structure and its supporting soil medium interact with one another to influence the behaviour of both. SSC normally leads to an increase in natural period of the structure, increased damping and an increase in lateral displacements of the structure. The effect of SSC is commonly ignored, because it is often a valid assumption. However, such effects can, in particular circumstances, be detrimental to the structure. The paper presents a simplified procedure for finding out the response of three-storey structure due to the effect of SSC. A simple practical method to assess the likely impact of SSC on the response of a MDOF structure is presented, which can help the researchers understand the detailed behaviour of soil and structure during seismic events. Detailed step-by-step procedure is presented by solving a numerical problem.

An Improved Probabilistic Seismic Hazard Assessment of Tripura, India

The State of Tripura lies in northeast India which is considered to be one of the most seismically active regions of the world. In the present study, a realistic Probabilistic Seismic Hazard Assessment (PSHA) of Tripura State based on improved seismogenic sources considering layered polygonal sources corresponding to hypo-central depth range of 0 to 25 km, 25 to 70 km and 70 to 180 km, respectively and data driven selection of suitable Ground Motion Prediction Equations (GMPEs) in a logic tree framework is presented. Analyses have been carried out by formulating a layered seismogenic source zonation together with smooth-gridded seismicity. Using the limited accelerogram records available, most suitable GMPEs have been selected after performing a thorough quantitative assessment and thus the uncertainty in selecting appropriate GMPEs in PSHA has been addressed by combining them with proper weight factor. The computations of seismic hazard are carried out in a higher resolution of grid interval of 0.05 $\degree$ X 0.05 $\degree$. The probabilistic seismic hazard distribution in terms of Peak Ground Acceleration (PGA) and 5% damped Pseudo Spectral Acceleration (PSA) at different time periods for 10% and 2% probability of exceedance in 50 years at engineering bedrock level have been presented. The final results show significant improvements over the previous studies, which is reflecetd in the local variation of the hazard maps. The design response spectra at engineering bedrock level can be computed for any location in the study region from the hazard distributions. The results will be useful for earthquake resistant design and construction of structures in this region.

Probabilistic Seismic Hazard Analysis of Hazara Kashmir Syntaxes and its Surrounding

Abstract The Hazara Kashmir syntaxes (HKS) is located in the western Himalayas in Pakistan that marks the easternmost proximity of the western Himalayan mountain system and is regarded as one of the most tectonically active domains of the world. In this study, the seismic ground motion parameters have been calculated for Hazara Kashmir syntaxes and its surrounding. The seismic hazard parameters were computed using probabilistic seismic hazard analysis (PSHA) and the standard Cornell–McGuire method at each grid spacing of 0.1o × 0.1o. This study encompasses the seismic records of the historical and instrumental database to establish the recurrence relationship based on an appropriate ground motion prediction equation (GMPE). Recently developed, the Boore and Atkinson (2008) next-generation attenuation (NGA) and Akkar and Bommer (2007) attenuation relationships were adopted for hazard computation. The resultant peak ground acceleration (PGA) maps and spectral intensity curves at T = 0.05 to T = 3, for 100, 250, 475, 1000, and 2500 year return periods have been estimated at bedrock level. This study concludes that the seismic provision for the building code of Pakistan needs to be revised and updated.

Effect of Declustering Algorithm in Probabilistic Seismic Hazard Analysis for Kathmandu Valley

An earthquake is a random event with uncertainty on time of occurrence, size of events, and location of rupture. So earthquake phenomenon is a model based on Poisson’s distribution. Thus, all the dependent event like foreshock and aftershock has to be removed before performing any Probabilistic Seismic Hazard Analysis (PSHA). Among the number of methodologies proposed for declustering methods, the process proposed by Gardener and Knopoff (1974) and Reasenberg (1985) was mostly used due to the availability of source code and reliability of declustering work. In this study, an attempt has been made to compare the effect of the declustering process at hazard level for the scenario of Kathmandu Valley. Probabilistic seismic hazard analysis of Kathmandu valley is performed using RCRISIS software with different seismicity parameters calculated for without declustering, declustering using Gardener and Knopoff (1974), and declustering using Reasenberg (1985). Calculated PGA value at bedrock level for 760 years return period for three declustering models compared with the measured square root of the sum of square (SRSS) PGA by 2015 Gorkha earthquake at Kathmandu valley at KTP station. Obtained results highlighted the suitability of the Gardener and Knopoff source code for the study area.

Development of an Interpolation Scheme for Seismic Indexes in Lima Metropolitan, Peru

In recent years, the development of seismic networks in Metropolitan Lima, administrated by public and private institutions, has received special attention since it makes possible the quantification of different seismic indexes under the occurrence of earthquakes. Therefore, the integration of the information both from acceleration sensors and site conditions from microzoning studies allows the estimation of the possible extent of the damage in quasi-real time. In this study, the implementation of a system to evaluate seismic parameters in a uniform grid of 250 x 250 m2 resolution is reported. In this regard, peak ground acceleration (PGA) values from the available time-history records are computed and reduced to the engineering bedrock level. Then, by means of the interpolation technique called Ordinary Kriging, in which each seismic station is considered as a random variable and the correlation between a pair of such random variables depends only on the distance between their coordinates, the acceleration distribution is evaluated. Amplification factors are applied in order to finally bring the PGA up to the surface level. A quantitative evaluation of the accuracy of our results is performed using two recent earthquakes with moment magnitude larger than 5: the 2019 Mw 8.0 Lagunas earthquake and 2021 Mw 6.0 Mala earthquake. The results have reproduced to some extent the seismic response of the diverse geomorphological deposits in Metropolitan Lima and suggest the inclusion of a larger number of strong motion stations in order to reduce the estimation errors.

Deterministic Seismic Hazard Analysis of Bharuch City and Surrounding Region

The research of seismic hazards along with their preparedness is critical for the development of structures which are both safe and economically effective. Ankleshwar, also known as the "Chemical Capital of India," is located in Bharuch district situated on Gujarat's south-west coast and it is categorised as seismic zone III by the Indian seismic zonation system. Past earthquake data and accessible seismotectonic information were used to conduct a deterministic seismic hazard study of the Bharuch region. After processing earthquake data obtained from 1819 to 2019, a separate seismic catalogue encompassing a 400-kilometer radius around Bharuch city was created. To get rid of the dependent events, the complete catalogue was declustered. Using basic mathematical procedures, the minimum distances from every seismic source generating tectonic activity were estimated. Predictive correlations for the region were used to estimate the Peak Ground Acceleration (PGA) values at bedrock level. The present analysis shows that with a maximum probable earthquake of magnitude 5.8 triggered by the Narmada Son Fault (NSF), the values of PGA of Bharuch region have ranged from 0.086 to 0.51 g. The key design parameters for the Bharuch city and surrounding region are provided by the PGA model discussed in this study.

A case study on the application and workability of the crosshole seismic survey in a karstic area

Crosshole seismic tomography is currently one of the reliable methods used in identifying the seismic velocity patterns for the development in areas challenged by presence of karstic features due to dissolution of the underlying limestone bedrock formation. The crosshole seismic tomography which provides a persistent image of the borehole and its surroundings in the form of P-wave velocity, picks up in-depth information compared to other surface geophysical methods. A crosshole seismic survey which consists of 99 lines connecting a total of 48 boreholes were conducted at Jalan Cochrane for a proposed residential development to determine the subsurface geology of the area. The site was divided into four main towers, namely Tower A and B (East) and Tower A and B (West). Jalan Cochrane is underlain by the Kuala Lumpur Limestone formation. This survey was mainly conducted to identify the possible cavities and incompetent rocks which are fractured and infilled in the proposed area. The crosshole seismic survey tomography correlated well with the borehole information obtained. Several drop in velocity observed were concluded to be possible cavities in the bedrock. Data obtained in Tower A and B (West) are more uniform and have a uniform bedrock level compared to the data in Tower A and B (East) which has an undulating bedrock level as well as fractured rocks and infilled cavities. This paper presents the findings obtained from the crosshole seismic survey conducted at Jalan Cochrane which successfully mapped out the cavities and bedrock level.

Application of Artificial Intelligence Techniques for the Determination of Groundwater Level Using Spatio-Temporal Parameters.

Increasing the depth of mining leads to the location of the mine pit below the groundwater level. The entry of groundwater into the mining pit increases costs as well as reduces efficiency and the level of work safety. Prediction of the groundwater level is a useful tool for managing groundwater resources in the mining area. In this study, to predict the groundwater level, multilayer perceptron, cascade forward, radial basis function, and generalized regression neural network models were developed. Moreover, four optimization algorithms, including Bayesian regularization, Levenberg–Marquardt, resilient backpropagation, and scaled conjugate gradient, are used to improve the performance and prediction ability of the multilayer perception and cascade forward neural networks. More than 1377 data points including 12 spatial parameters divided into two categories of sediments and bedrock (longitude, latitude, hydraulic conductivity of sediments and bedrock, effective porosity of sediments and bedrock, the electrical resistivity of sediments and bedrock, depth of sediments, surface level, bedrock level, and fault), and besides, 6 temporal parameters are used (day, month, year, drainage, evaporation, and rainfall). Also, to determine the best models and combine them, 165 extra validation data points are used. After identifying the best models from the three candidate models with a lower average absolute relative error (AARE) value, the committee machine intelligence system (CMIS) model has been developed. The proposed CMIS model predicts groundwater level data with high accuracy with an AARE value of less than 0.11%. Sensitivity analysis indicates that the electrical resistivity of sediments had the highest effect on the groundwater level. Outliers’ estimation applying the Leverage approach suggested that only 2% of the data points could be doubtful. Eventually, the results of modeling and estimating groundwater level fluctuations with low error indicate the high accuracy of machine learning methods that can be a good alternative to numerical modeling methods such as MODFLOW.

Probabilistic Seismic Hazard Assessment at Bedrock Level Using a Logic Tree Approach: A Case Study for Odisha, an Eastern State of India

Probabilistic Seismic Hazard Assessment at Bedrock Level Using a Logic Tree Approach: A Case Study for Odisha, an Eastern State of India