Strong-motion Accelerograms Research Articles

Development of repairability index for steel moment frames with post-tensioned self-centering connections

With regard to the effects of self-centering structural performance in reducing damages in the event of an earthquake, in this study an attempt is made at developing a repairability index for post-tensioned self-centering steel moment connections. Based on the 18 structural models studied, a building in which the maximum connection rotation does not exceed the allowable rotation of the immediate occupancy level is considered repairable. Accordingly, the output data of Incremental Dynamic Analyses have been depicted in OpenSees under 22 sets of near and far-field strong ground motion accelerograms based on connection relative rotation and spectral acceleration the Repairability Index of Self-Centering Frame (RISCF) will be obtained. For input of spectral acceleration of the first mode of the structure in the repairability equation, if this amount is smaller than 1, the aim of repairability is met. In order to qualitatively evaluate angle damages, the Angle Failure Probability of Self-centering Frame (AFPSCF) will be depicted with regard to the fragility curve, if the number is less than 1, the building can return to its previous performance level with angle replacement after the event of an earthquake.

Innovative EC8-compliant solutions for selection of the optimum retrofitting scheme of buildings with special characteristics

This article presents the seismic assessment and retrofit design of an existing old building in Greece of great regional importance. The Building is the “Administration building of Kalamata” located in the city of Kalamata, capital of the Messinia Prefecture. The Building, the largest in the city, is a seven-floor reinforced concrete (r/c) structure with a basement built in 1974. The seismic assessment procedure is based on the provisions of the EN 1998-3 code and the Greek code for structural interventions “KAN.EPE.,” introducing several novelties that give solutions to difficult practical problems with respect to the modeling, the analysis methods, and performance evaluation framework. The article presents details of the Building’s modeling, description of the analyses, and the corresponding results, as well as the most efficient retrofitting schemes that fulfill the safety demands (i.e. performance level B or “Life safety” and performance level C or “Collapse prevention” according to KAN.EPE.), considering cost and minimal disturbance both for the superstructure and foundation interventions. While considering the various intervention solutions, it proceeds with new simplified ways that optimize the proposed solution. As such, it can be used as a paradigm for finding clever, practical, and at the same time economical solutions. An interesting characteristic of the Building is that it has been strengthened already after the damaging earthquake of 1986, but the new usage requirements raised questions about the adequacy of that earlier strengthening. Last, but not least, it must be mentioned that this building is unique in the sense that the main earthquake record (a strong motion accelerogram) obtained during the damaging 1986 Kalamata earthquake was at its basement. This record is also used for the assessment.

Probabilistic seismic hazard mapping of National Capital Region of India using a modified gridded seismicity model

This is the first comprehensive study for a seismic macro-zonation of the National Capital Region of India by using the probabilistic seismic hazard analysis approach. A modified gridded seismicity model is used for this purpose, in which the earthquake occurrence rates obtained using the Gutenberg-Richter's (G-R) relationships for conventional area type seismic sources are distributed non-uniformly among a grid of cells. This provides a more robust approach than the commonly used weighted sum of area sources of homogeneous seismicity and the zone-free smoothed gridded seismicity. Other distinguishing features of the present analysis include: detailed seismotectonic evaluation of the region to identify seven area type seismic sources, compilation of a comprehensive earthquake catalogue for the estimation of seismicity recurrence parameters, selection of the most appropriate ground motion prediction equation by using a database of 71 strong motion accelerograms recorded in the region, and estimation of the compatible distance parameters by associating a fictitious fault rupture plane to each grid cell with appropriate strike and dip angles. Hazards maps are prepared for the hard rock site condition in terms of the peak ground acceleration and the 5%-damping acceleration response spectrum amplitudes for several combinations of natural periods and return periods. A simple empirical approach is also developed to obtain amplification factors for modifying the uniform hazard response spectra for the rock sites to those for the soil sites with a given VS30 value. The hazard estimates from this study are found to be somewhat higher with greater site-to-site variations as compared to those from the earlier studies.

Strong Ground Motion Simulation for Forecasting the Probable Seismic Impacts in the Territory of the Republic of North Ossetia–Alania

Abstract—The models based on the empirical data are proposed for probabilistic forecasting the characteristics of strong ground motions (SGM) from the earthquakes, potentially dangerous for the territory of the Republic of North Ossetia–Alania. We consider the models of SGM characteristics that are most important in the engineering practice (macroseismic intensities of ground shaking, peak ground accelerations, periods, durations, spectra, and strong-motion accelerograms) in the vicinity of the sources of earthquakes of different magnitudes and at different distances from the sources in application to the seismogeological conditions of the study region. The models are developed using both the conventional statistical analysis of a large amount of data on instrumental recording and macroseismic description of the strong and perceivable earthquakes in the Caucasus and other seismically active regions of the world and a new method for reconstructing the spectra of the strong earthquakes from their macroseismic field. The cross-comparison of the estimates obtained based on the proposed models with each other and with the estimates obtained by the other authors has shown that they are fairly realistic and reliable.

Automatic Extraction of Permanent Ground Offset from Near-Field Accelerograms: Algorithm, Validation, and Application to the 2004 Parkfield Earthquake

ABSTRACTPermanent ground offsets, constituting a prime dataset for constraining final fault-slip distributions, may not be recovered straightforwardly by double integration of near-field accelerograms due to tilt and other distorting effects. Clearly, if a way could be found to recover permanent ground offsets from acceleration records, then static datasets would be enlarged, and thus the resolution of fault-slip inversions would be enhanced. Here, we introduce a new approach for extracting permanent offsets from near-field strong-motion accelerograms. The main advantage of the new approach with respect to previous ones is that it corrects for source time functions of any level of complexity. Its main novelty is the addition of a constraint on the slope of the ground velocity spectra at long periods. We validated the new scheme using collocated accelerograms and Global Navigation Satellite Systems (GNSS) records of the 2011 Mw 9 Tohoku-Oki earthquake. We find a good agreement between accelerogram-based and GNSS-based ground offsets over a range of 0.1–5 m. To improve the spatial coverage of permanent ground offsets associated with the 2004 Parkfield earthquake, near-field accelerograms were baseline corrected using the new scheme. Static slip inversion of the combined GNSS-based and accelerogram-based ground displacements indicates appreciable seismic moment release south of the epicenter, about 5 km into the Cholame section of the San Andreas fault. We conclude that the strong shaking observed to the south of the epicenter is directly related to the slip in that area and is not the result of local amplification.

Selection of earthquake ground motion accelerograms for structural design in Hong Kong

Hong Kong is situated in an intraplate area of low to moderate seismicity, where recorded strong-motion accelerograms are scarce. As part of the seismic design process, dynamic time-history analysis is sometimes required for assessing the seismic performance of structures. Hence, earthquake accelerograms representative of various local design hazard levels are needed. This study aims to develop a methodology for building up a database of earthquake accelerograms for the Hong Kong region which can be used for the analysis and design of a variety of structural and geotechnical systems. An outline of the previous probabilistic seismic hazard analysis studies conducted for Hong Kong is first presented and several design earthquake scenarios are determined, which contribute most to the local seismic hazard given a specific return period. The median response spectra and conditional mean spectra of the selected earthquake scenarios for reference rock sites are then derived based on the component attenuation model. The conditional mean spectra are then used as the target spectra for the selection and scaling of recorded accelerograms sourced from the available global database. Finally, a suite of conditional mean spectra–compatible accelerograms for rock sites is presented, from which event-specific and site-specific accelerograms are generated through dynamic site response analysis.

THE ROLE OF SEISMIC POUNDING IN THE OPTIMAL SELECTION OF GROUND-MOTION INTENSITY MEASURES

To grant quantitative estimates of the expected levels of seismic ground motion as the primary input to seismic hazard assessments, it is vital to characterize the complicated nature of strong motion accelerograms using simple indices. Over the years, numerous ground-motion parameters have been suggested by researchers for that purpose, and to be used as indices of a ground motion’s damage potential. Finding a best correlated ground-motion parameter with the damage index, is a main goal of such type of studies. Minimizing the variability in this correlation is of great importance to determine the expected damage with a higher degree of accuracy. This paper presents an analysis of different ground-motion intensity measures (IMs) that can be used in assessing the performance of reinforced concrete buildings to test the impact of pounding on the optimal selection of ground-motion IMs. The occurrence of structural pounding in metropolitan cities is caused by the inadequate gap between adjacent buildings. Identifying the function in which the seismic pounding performs in selecting the most appropriate ground-motion IM, as an illustration of seismic action in a region of interest, is a main objective of the current study. Special cases of typical two-dimensional adjacent multi-story reinforced concrete buildings are analyzed using a number of natural earthquake time histories. The results indicated that, based on the number of records, the variability in the gap distance between buildings may lead to the selection of different IMs.

Empirical Attenuation relationship for Peak Ground Horizontal Acceleration for North-East Himalaya

Empirical Attenuation relationship for Peak Ground Horizontal Acceleration for North-East Himalaya

A preliminary empirical model for frequency-dependent attenuation of Fourier amplitude spectra In Serbia from the Vrancea earthquakes

We present the frequency-dependent attenuation model for Fourier amplitude spectra of strong earthquake ground motion in Serbia from intermediate depth earthquakes in the Vrancea source zone in Romania. The development of this type of scaling is the essential first step toward developing the corresponding attenuation and scaling equations for pseudo relative velocity spectra (PSV), which are necessary for seismic macro- and microzoning in the territory of Serbia. Such scaling is necessary because the Vrancea source zone produces large earthquakes with shaking that attenuates differently from the local earthquakes in Serbia. Development of such a scaling model is associated with several difficulties, the principal one being the lack of recorded strong motion accelerograms at epicentral distances exceeding 300km. To reduce uncertainties with such scaling, we require our preliminary scaling equations to be consistent with independent estimates of seismic moment, stress drop, and radiated wave energy. In the future, when the recorded strong motion data from Vrancea earthquakes increases several-fold of what it is today, it will become possible to perform this analysis again, thus leading to more reliable and permanent scaling estimates.

Triggered slip on a back reverse fault in the Mw6.8 2013 Lushan, China earthquake revealed by joint inversion of local strong motion accelerograms and geodetic measurements

The 2013 Mw6.8 Lushan, China earthquake occurred in the southwestern end of the Longmenshan fault zone. We jointly invert local strong motion data and geodetic measurements of coseismic surface deformation, including GPS and InSAR, to obtain a robust model of the rupture process of the 2013 Lushan earthquake. Our joint inversion best model involves the rupture of two opposing faults during the Lushan earthquake, a main fault and a secondary fault. It is only when the secondary fault is included that both the GPS and InSAR measurements are fit along with the near-field strong motion. Over 75% of the computed moment was released in slip on the main fault segment, a northwest dipping, listric thrust fault, with buried thrust and dextral strike-slip at hypocenter depths, and with only minor slip closer to the surface. The secondary fault mainly involved oblique thrust slip or pure dextral strike-slip at shallower depths, and accounts for just under 24% of the moment released in the Lushan earthquake. Coulomb stress changes of about 0.5MPa on the secondary fault segment at the time coseismic slip initiated on that fault indicate that slip was likely triggered by the coseismic slip on the main blind thrust fault. Our coseismic slip model is consistent with a sub-horizontal and east–west to southeast–northwest trending most compressive stress. Our inferred coseismic slip model is also consistent with previous GPS derived models of strain accumulation on the Longmenshan fault system.

An Improved Approach for Nonstationary Strong Ground Motion Simulation

A new stochastic ground motion model for generating a suite of ground motion time history with both temporal and frequency nonstationarities for specified earthquake and site characteristics is proposed based on the wavelet method. This new model is defined in terms of 6 key parameters that characterize the duration, evolving intensity, predominant frequency, bandwidth and frequency variation of the ground acceleration process. All parameters, except for peak ground acceleration (PGA), are identified manually from a database of 2444 recorded horizontal accelerations. The two-stage regression analysis method is used to investigate the inter- and intra-event residuals. For any given earthquake and site characteristics in terms of the fault mechanism, moment magnitude, Joyner and Boore distance and site shear-wave velocity, sets of the model parameters are generated and used, in turn, by the stochastic model to generate strong ground motion accelerograms, which can capture and properly embody the primary features of real strong ground motions, including the duration, evolving intensity, spectral content, frequency variation and peak values. In addition, it is shown that the characteristics of the simulated and observed response spectra are similar, and the amplitude of the simulated response spectra are in line with the predicted values from the published seismic ground motion prediction equations (SGMPE) after a systematic comparison. The proposed method can be used to estimate the strong ground motions as inputs for structural seismic dynamic analysis in engineering practice in conjunction with or instead of recorded ground motions.

Preliminary Report on the 22 November 2014Mw 6.1/Ms 6.3 Kangding Earthquake, Western Sichuan, China

Online Material: Relocated aftershock catalog figures of moment rate function, magnitude–time distribution, observed strong-motion accelerograms, spectral accelerations versus period, and photos of damaged buildings. The M s 6.3 ( M w 6.1) Kangding earthquake struck western Sichuan Province on 22 November at 08:55:27 UTC (16:55:27 p.m. local time). Its epicenter was located approximately 37 km northwest of Kangding country and 236 km southwest of Chengdu city. The China Earthquake Networks Center (CENC) reported that the epicenter was located at 30.3° N, 101.7° E with a hypocentral depth of 18 km (Fig. 1). Three days after the first shock, another moderate earthquake ( M s 5.8/ M w 5.7) hit the area to the southeast. The distance between the two events is about 10 km. Detailed information of this earthquake is available on the website of China Earthquake Administration (CEA) (http://www.cea.gov.cn/publish/dizhenj/468/553/101420/index.html; last accessed December 2014, in Chinese) and on the website of U.S. Geological Survey (http://earthquake.usgs.gov/earthquakes/eventpage/usb000syy0; last accessed December 2014). The Kangding earthquake was located near the left-lateral, strike-slip Xianshuihe fault system (Allen et al. , 1991). The mainshock was characterized by a strike-slip mechanism, with two nearly vertical nodal planes striking approximately north-northwest and northeast-east, respectively. The maximum intensity was VIII on the Chinese intensity scale (http://en.wikipedia.org/wiki/China\_Seismic\_Intensity_Scale; last accessed December 2014), with the areas above intensity VI being 11,060 km2. The earthquake caused 5 deaths and 80 injuries. The direct economic loss has been estimated as more than 4.2 billion Renminbi (RMB; or about $0.7 billion U.S.). Figure 1. Tectonic blocks and strong earthquakes since 1997 in the Tibetan plateau. Dashed rectangle indicates the region in Figure 2. Large red arrow indicates the crustal motion direction. Black-and-white circles are the focal mechanism of recent strong earthquakes with magnitude larger than M s 7.0. Red-and-white circles are the focal mechanism of the M s 6.3 and 5.8 Kangding …

Review on Baseline Correction of Strong-Motion Accelerogram

Because of various reasons, the baseline drift in the strong motion accelerogram was often founded, especially in the near-fault accelerogram. The baseline drift could lead to the unreliable velocity and displacement obtained by the accelerogram integration without or with improper specialized baseline correction. For dealing with the problem, in the study, the various reasons causing the baseline drift in accelerogram were analyzed, the baseline correction principle and the different baseline correction methods were discussed, and the problems in the methods were pointed out.

Magnitude Estimation for the 2011 Tohoku-Oki Earthquake Based on Ground Motion Prediction Equations

This study investigates whether real-time strong ground motion data from seismic stations could have been used to provide an accurate estimate of the magnitude of the 2011 Tohoku-Oki earthquake in Japan. Ultimately, such an estimate could be used as input data for a tsunami forecast and would lead to more robust earthquake and tsunami early warning. We collected the strong motion accelerograms recorded by borehole and free-field (surface) Kiban Kyoshin network stations that registered this mega-thrust earthquake in order to perform an off-line test to estimate the magnitude based on ground motion prediction equations (GMPEs). GMPEs for peak ground acceleration and peak ground velocity (PGV) from a previous study by Eshaghi et al. in the Bulletin of the Seismological Society of America 103. (2013) derived using events with moment magnitude (M) ≥ 5.0, 1998–2010, were used to estimate the magnitude of this event. We developed new GMPEs using a more complete database (1998–2011), which added only 1 year but approximately twice as much data to the initial catalog (including important large events), to improve the determination of attenuation parameters and magnitude scaling. These new GMPEs were used to estimate the magnitude of the Tohoku-Oki event. The estimates obtained were compared with real time magnitude estimates provided by the existing earthquake early warning system in Japan. Unlike the current operational magnitude estimation methods, our method did not saturate and can provide robust estimates of moment magnitude within ~100 s after earthquake onset for both catalogs. It was found that correcting for average shear-wave velocity in the uppermost 30 m ( $$ V_{{{\text{s}}_{30} }} $$ ) improved the accuracy of magnitude estimates from surface recordings, particularly for magnitude estimates of PGV (Mpgv). The new GMPEs also were used to estimate the magnitude of all earthquakes in the new catalog with at least 20 records. Results show that the magnitude estimate from PGV values using borehole recordings had the smallest standard deviation among the estimated magnitudes and produced more stable and robust magnitude estimates. This suggests that incorporating borehole strong ground-motion records immediately available after the occurrence of large earthquakes can provide robust and accurate magnitude estimation.

The 2011 Lorca seismic series: Temporal evolution, faulting parameters and hypocentral relocation

The Lorca 2011 seismic series was recorded by an unprecedented set of high quality on scale broadband seismograms and strong motion accelerograms. The waveforms from permanent and temporary broadband seismic networks deployed in the region by different institutions allowed to invert regional moment tensor for the fore, main and largest aftershock of the complete seismic sequence. Using double-difference algorithm we have performed a precise relocation of the seismic series, where body wave travel times from strong ground motion accelerograms were included in the data set. Regional moment tensor inversion for the three main events show similar oblique-reverse faulting regime with a northeast-southwest fault orientation. The scalar seismic moment, moment magnitude and focal depth retrieved from the inversion yield the following values for each event: \(\hbox {Mo}=6.5\times 10^{16}\) Nm (Mw = 5.2) for the mainshock, \(\hbox {Mo}= 9.6 \times 10^{15}\) Nm (Mw = 4.6) for the foreshock and \(\hbox {Mo}=7.3\times 10^{14}\) Nm (Mw = 3.9) for the large aftershock. The centroid depths range between 4 and 6 km. The double-difference relocation of the seismic series shows significant epicentral differences with the preliminary routine location. The epicentral solutions given by this relocation show a seismic sequence distributed following a NE–SW strike, subparallel to the Alhama de Murcia fault and compatible with the faulting parameters inverted from the moment tensor analysis. The hypocenters of the series generate a subvertical trend in depth distribution, being concentrated between 2 and 6 km. The depth distribution of the main events, which range from 4.6 to 5.5 km, is in good relationship with the faulting and depth parameters deduced from the moment tensor inversion technique. The regional moment tensor solutions for the three largest earthquakes, the epicentral distribution and the focal depths show good relationship with the surface geometry and tectonic regime of the Alhama de Murcia fault. The stress drop deduced for the mainshock gives a value ranging between 58 and 85 bars, which does not support the idea of a high stress drop release as a main factor contributing to the high ground acceleration recorded at Lorca. The PGA values observed at Lorca, which contributed to the high damage independently of structural deficiencies, could be generated mainly by shallowness and proximity to the seismic source together with a directivity effect in the seismic radiation.

Characteristics of observed strong motion accelerograms from the 2011 Lorca (Spain) Earthquake

The Lorca earthquake (southeast Spain) on May 11, 2011; Mw 5.1, and its aftershocks, have provided an important set of accelerograms recorded by the strong motion network of the Instituto Geografico Nacional of Spain. It is particularly noticeable that the record obtained in Lorca town, very near of the fault rupture, presents a PGA value close to 0.37 g in the N30W component. This paper provides an overview of the strong motion data recorded during the Lorca seismic series, with particular attention to the accelerograms from the mainshock and foreshock and its characteristics. Due to the special circumstances of these two records, a more detailed processing has been required, in which various alternatives to adjust the baseline have been considered and analyzed. Based on this special processing, small residual displacements were obtained and reported in some of these cases. However, given the sensitivity of the process and the small obtained values, these findings should be taken with caution. Besides, response spectra have been analyzed and compared with design spectra proposed by the Spanish Seismic Code (NCSE-02) for the towns of Lorca, Alhama de Murcia and Mula. Large amplitude differences were observed in these spectra if compared to those recorded in Lorca. Also noteworthy is that the design spectra proposed for this town were exceeded by some horizontal directions of the response spectra.

Using Borehole Records to Estimate Magnitude for Earthquake and Tsunami Early-Warning Systems

This paper presents a new application of the ground‐motion prediction equations (GMPEs) to estimate the event magnitude for earthquake and tsunami early warning systems. This technique incorporates borehole strong‐motion records along with surface recordings provided by Kiban Kyoshin network (KiK‐net) stations. We analyzed strong ground motion data from earthquakes with moment magnitude ( M ) ranging from 5.0 to 8.1 recorded by KiK‐net stations provided by Japan’s National Research Institute for Earth Science and Disaster Prevention (NIED) over the interval of 1998 to 2010. We used 2160 strong ground motion accelerograms with peak ground acceleration (PGA) larger than 10 cm/s2 recorded by borehole seismographs, and 890 waveforms with PGA larger than 80 cm/s2 recorded by surface seismographs to derive GMPEs for PGA and peak ground velocity (PGV) in Japan. These GMPEs are used as the basis for regional magnitude determination. Predicted magnitudes from PGA values (MPGA) and predicted magnitudes from PGV values (MPGV) were defined separately for borehole and surface recordings. MPGA and MPGV strongly correlate with the moment magnitude of the event, provided that at least 20 records for each event are available. The results show that MPGV from borehole data has the smallest standard deviation among the estimated magnitudes and provides an accurate early assessment of earthquake magnitude. We demonstrate that incorporation of borehole strong ground motion records immediately available after the occurrence of large earthquakes significantly increases the accuracy of earthquake magnitude estimation and improves earthquake and tsunami early warning systems performance.

Effects of shallow and deep geology on seismic hazard estimates: a case study of pseudo-acceleration response spectra for the northwestern Balkans

Northwestern Balkans represents one of the rare regions where data on both the shallow geology (i.e., local soil conditions) and the deep geology exist for stations that recorded hundreds of strong motion records. The strong motion database used in this study consists of 203 strong motion accelerograms (each with three orthogonal translational components), recorded in former Yugoslavia in the period 1976–1983, from 108 contributing earthquakes. In this paper, the results of a series of regression analyses are presented where empirical equations for scaling pseudo-acceleration response spectra were developed on the basis of 5 subsets of data and using three prediction models. Results of the regression analyses show that for ground motion in the horizontal direction, both the shallow and deep geology site conditions have to be taken into account or else the spectral estimates might be considerably biased. Results show that the shallow geology influences spectral amplitudes the most in the short period range and has much lesser effects for larger periods, while the influence of the deep geology is expressed in a wider range of intermediate to long periods. Results also show that if the prediction model that considers solely the shallow geology effects is used, the spectral peaks that have been related to the deep geology effects will completely vanish for larger source-to-site distances, while in the case when solely the deep geology is considered, the peaks related to the shallow geology will not be visible for any distance. As for the amplitudes in the vertical direction, although both the shallow and the deep geology effects are less expressed than in the horizontal one, they still cannot be neglected—the deep geology effects are visible for a wider range of vibration periods, while the shallow geology has some effects only for periods smaller than ~0.3 s.

A non-parametric wave type based model for real-time prediction of strong ground motion accelerogram

A wave type based method for real-time prediction of strong ground motion (SGM) accelerogram is developed. Real-time prediction of SGM is requested in predictive building control systems to trigger and control actuator systems achieving the goal of reduction of the structural deformations during an on-going earthquake. It is well known that SGM is a classic example of non-stationary stochastic process with temporal variation of both amplitude and frequency content. The developed non-parametric model considers the non-homogeneity of the seismic process which contains different wave types with the individual frequency contents and time-dependency amplitude distribution pattern. Therefore, an important part of the method is to detect dominant seismic wave phases. Prediction of seismic signal is undertaken by applying frequency adaptive windowing approach, which leads to predict the on-coming signal in time window t+Δt based on the measured data in the time window t. Besides use of the frequency adaptive windowing, constant windowing and semi-adaptive windowing approaches are deployed. The results show that use of the adaptive time windows relevant to dominant frequency of the signal will enable the model to catch and predict the most dominant frequencies. Performance of the proposed model is verified by the use of 97 free-field accelerograms, which were applied to train and validate the prediction model. The selected accelerograms were measured above the soil type C and D according Eurocode 8 and their Moment magnitude are ranging between 6.2 and 7.7. The learning capability of the radial basis function Artificial Neural Network is used to reconstruct the SGM accelerogram. The most significant advantage of the proposed model is the concept of wave type based modeling which has the advantage of a conceptual physical modeling of the seismic process. Comparison of the real-time predicted and the observed accelerograms shows a high correlation when the frequency adaptive approach is applied. This paper lays a foundation for more effective use of real-time predictive control systems and potential for future extension in active structural control as well as in real-time seismology.

Seismological model parameters for northeastern and its surrounding region of India

A point source seismological model is used in this study to model the available strong motion accelerograms recorded by 17 events and to calculate three seismological model parameters, the source, path, and quality factor. Due to the paucity of recorded events, this is the first time these model parameters have been obtained for the northeastern and its surrounding region of India. The quality factors of the horizontal and vertical components of recorded events with corresponding standard deviations are QH(f) = 188.55f0.94, σ1 value (25, 0.025) and QV(f) = 169.76f0.93, σ1 value (20, 0.03), respectively. The source parameter stress drop values (Δσ) vary within 124–180 bars for the subduction region and 80–169 bars for the active region. The Kappa factors for the horizontal and vertical components of recorded events on the soft rock site are 0.06 and 0.05, respectively. These seismological model parameters obtained in this study will be useful for future work deriving a ground motion attenuation relation based on a spectral model. Finally, these results are useful for seismic hazard assessment of a region having sparsely recorded events.