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a Parametric comparison of actual and simulated PGA of the Bhutan earthquake and b Plot of actual and simulated PGA with epicentral distance (R) at BOK, BON, DIP, GOL, GUA, KOK, NON, TEJ stations. Black and grey line shows the attenuation characteristics of observed and simulated PGA values of observed and simulated records with epicentral distance, R
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On 21st September 2009 an earthquake of magnitude (Mw 6.1) occurred in the East Bhutan. This earthquake caused serious damage to the residential area and was widely felt in the Bhutan Himalaya and its adjoining area. We estimated the source model of this earthquake using modified semi empirical technique. In the rupture plane, several locations of...
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http://www.zoobank.org/urn:Isid:zoobank.org:act:C1E4EFED-70F6-4E6D-844F-2BE62EB741F5
Citations
... A step-by-step procedure of the method is described in the following section. This method yields good results for ground motions of several earthquakes such as 1999 Chi-Chi earthquake (Rajaram, 2016), 1991Uttarkashi earthquake, 2009 Bhutan earthquake (Sandeep et al., 2017), 2013 Doda earthquake (Rajaram and Pradeep, 2016) and 2013 Pakistan earthquake (Rajaram and Pradeep, 2020). The main objective of the study is to find out the efficacy of the method for Alaska region. ...
An effective earthquake (Mw 7.9) struck Alaska on 3 November, 2002. It ruptured 340 km along three faults namely, the Susitna Glacier, Denali and Totschunda faults in central Alaska. The earthquake was recorded at 23 stations in Alaska and the Peak Ground Acceleration (PGA) of 0.32g was recorded at station PS10, which was located 3 km from the fault rupture. In this study, strike-slip Denali fault has been considered for studying the characteristics of ground motions through modified semi-empirical approach. The ground motion records of the 2002 Denali earthquake are generated through MATLAB code. The results revealed that modified semi-empirical approach is fairly good in agreement with observed ground motion records at all stations. A perfect match is observed between Fourier amplitude spectra of simulated and observed ground motions at PS09 and CARLO stations. A good match is observed between elastic response spectra of observed and simulated ground motions.
In the present study, a hypothetical earthquake of magnitude 8.5 has been simulated using the modified hybrid technique. Existing hybrid technique, as the name suggests, is the blend of two already existing simulation techniques, i.e. composite source technique and the envelope technique. In the present modified technique, site response functions and high-frequency decay parameter (kappa factor) have also been introduced in the existing hybrid technique. The waveforms have been simulated at more than 430 points using the calculated site response or transfer function estimated at 50 recording stations situated in the central seismic gap (CSG) region of Himalaya. Peak ground acceleration (PGA) and duration parameters have been estimated. Calculated PGA values helped estimating in the corresponding intensity for those PGA values at various stations. With the help of these PGA and intensity values, the scenario hazard map has been prepared for central seismic gap (CSG) region of Himalaya. It has been found that the stations situated close to rupture initiation point is ≥ 1 g. The estimated PGA values have been compared with the PGA values of other studies. The earthquake has been simulated using three different rupture points The station having highest PGA values changed with rupture initiation point. The intensity values are correlated with the damage pattern of region and therefore relatively more useful for agencies involved in the mitigation of seismic hazard of the region. Accordingly, the synthetic intensity maps have been generated in the present study by converting PGA values into MMI values using an empirical relation. The comparison with the other studies shows an agreement with the other studies. This modified technique is independent aftershocks database and velocity-Q structure. This research work will help bringing light on the effect of site response functions and kappa factor. This kind of study can help in mitigate the earthquake hazard and design an earthquake-resistant structures and building for that particular area.
Strong ground motion simulation is a reliable tool for seismic hazard assessment and mitigation of any region. The distribution of hazards during an earthquake is greatly influenced by the attenuation properties of the medium. Typically, regional attenuation characteristic is employed for strong motion simulation rather than site-specific attenuation. In the current study, the newly developed semi-empirical simulation approach is modified to use a site-specific attenuation relation. Initially, the medium attenuation characteristics are quantified by estimating frequency-dependent S-wave quality factor \(({Q_\beta}(f))\) at each recording station. These obtained \({Q_\beta}(f)\) relations at each station are further utilised to estimate the regional relation for the Garhwal and Kumaon regions as (90±4)f(0.86±0.05) and (54±2)f(0.89±0.1), respectively. These values suggest that the Garhwal region is relatively less attenuative and more credible for seismic hazards compared to the Kumaon region. The \({Q_\beta}(f)\) obtained at each recording station are further used to simulate the 1991 Uttarkashi (Mw 6.8) and 2011 Indo-Nepal (Mw 5.4) earthquakes. An improved match is perceived between the observed and simulated records with site-specific \({Q_\beta}(f)\) values instead of regional ones. This comparison successfully validates the present modification in SET. This work provides insight into getting more realistic simulated results and explores recent trends in strong motion seismology for seismic hazard evaluation.
A devastating earthquake (Mw 7.4) struck near Izmit city, northwestern Turkey, on 17 August 1999. The relatively large size of this earthquake and site amplification conditions caused severe damage in the Marmara region as well as the city of Istanbul. The disastrous outcome of this large earthquake requires careful analysis of the seismic hazard including local site effects in this region. Therefore, the present work addresses the issue of local site effects and modelling of strong ground motion for this earthquake. We have estimated the soil effects using the horizontal-to-vertical (H/V) ratio. Furthermore, high-frequency records are simulated using a modified semi-empirical technique (MSET) by including estimated site effects. This modification will provide more reliable and precise simulated strong motion records. In the present study, strong ground motions are simulated at nine seismic stations in the epicentral range of 40–99 km. These stations were selected based on their recorded data quality. To validate the technique, we have compared the synthetic records with the observed records in terms of root mean square error (RMSE). This comparison includes time records, pseudo-acceleration spectra, mean period and predominant period. This comparison shows MSET has successfully simulated the 1999 Izmit earthquake.
The 2016 Kumamoto earthquake (MJMA7.3) struck central area of Kyushu Island, Japan. The presence of near surface low velocity layer greatly amplified the ground motions and caused severe damage in this region. Therefore, it is essential to study the site characteristics of Kumamoto region. For this purpose, the present research article describes the modification in existing semi-empirical technique of strong motion simply by incorporating the site effect. These site effects are calculated using Horizontal to Vertical ratio (H/V) method. The estimated predominant frequencies (\(f_{{{\text{peak}}}}\)) for these stations varies between 2.5 and 7.5 Hz. The sites with low \(f_{{{\text{peak}}}}\) indicate higher soil thickness cover and hence, locations are more susceptible to damage. The station KMMH06 used in this work lies in close proximity to one of the major landslide locations (Minami Aso Village), triggered during this earthquake. The low to intermediate \(f_{{{\text{peak}}}}\) value estimated at KMMH06 proposes the area prone to site amplification and severe damage. Also, the initial location and parameters of rupture model of this earthquake are considered based on past seismicity and other empirical relations available. The detailed analysis proposes nucleation point in extreme NW corner of the rupture plane. Afterwards, the developed source model and modified technique compositely used to simulate high frequency records at eight near field stations. This includes time histories, response spectra, predominant period (Tp) and mean period (Tm). The above comparison successfully validates modified semi-empirical and source model for 2016 Kumamoto earthquake. As far as we are aware, this work is the first to model rupture plane of 2016 Kumamoto earthquake by means of modified semi-empirical technique. It provides adequately reliable results which will be advantageous for seismic hazard assessment of this region.
This study focuses on the validation and applicability of a recently modified semi-empirical technique (MSET) to integrate site effects. The improvement of MSET by considering site effects has been verified by the data of the 1988 Indo-Burma earthquake (Mw 7.2), which happened in the North Eastern Region (NER) in India. This technique is also used to model a future scenario earthquake (Mw 8.2) in the NER. The required site effects are estimated using Nakamura’s horizontal-to-vertical (H/V) ratio technique for 89 waveform records. The obtained site effects are further used to modify an existing semi-empirical technique. To validate this modification, the strong-motion records of the 1988 Indo-Burma earthquake are simulated for bedrock and surface conditions. Afterwards, the root mean square error (RMSE) of these records is compared with surface records obtained by 14 seismic stations. The records simulated at the surface are well validated well with observed ones as compared to the records simulated at bedrock and hence confirm the reliability of the MSET. The improved performance of the MSET after incorporation of site effects validates the approach of the present work and will prove to be significant for simulation of earthquake surface conditions in any region. Further, this improved MSET is used to simulate strong-motion records of a future scenario earthquake (Mw 8.2) with the same epicentral location. The iso-acceleration maps are prepared from simulated records for both cases (Mw 7.2 and 8.2), which provide peak ground acceleration (PGA) values of more than 500 and 1000, respectively, for near-field regions. The obtained results are of significant interest for seismic hazard assessment of NE India.
Earthquakes are one of the most destructive natural events worldwide. It represents a globally societal challenge necessitating practical and operational solution for reducing loss and mitigating risk. This can be realized through earthquake hazard and risk assessment. In this context, simulation of strong ground motion emerged as one of the indispensable prerequisites for earthquake resistant structure design. Hence, this chapter describes the recent progress and also pioneering efforts for the most prevalent simulation techniques including Stochastic simulation technique (SST), Empirical Green’s function technique (EGFT), Composite source modeling technique (CSMT) and Semi empirical technique (SET). Moreover, the detail analysis of each and every technique in terms of input parameters, output, advantages and limitations has been illustrated. To this end, we hope that this overview would help the seismologists and earthquake engineers to look at this area of study from different angles to reveal some hidden opportunities.
Strong motion studies continue to be a very active field in seismology, and the use of simulation techniques in this context will continue to be an important endeavour in the coming years. Therefore, this review summarizes the recent progress and also pioneering efforts for the most prevalent simulation techniques including stochastic simulation technique (SST), empirical Green’s function technique (EGFT), composite source modelling technique (CSMT) and semi-empirical technique (SET). Attempts are also made to analyse the impact of each and every technique in terms of input parameters, output, advantages and limitations. The detailed analysis of trends we discussed herein indicates that every technique has its own metiers and flaws; hence, it is very difficult to select a simulation technique for a particular task. In conclusion, we hope that this overview would help the seismologists and earthquake engineers to look at this area of study from different angles to reveal some hidden opportunities. This will serve as an inspiration to improve the existing techniques for seismic hazard analysis and modelling of future earthquakes.
The Iwate–Miyagi earthquake (Mw 6.9) of 14 June 2008 is one of the largest intraplate earthquakes that struck north-east Japan. This earthquake has produced the largest peak ground acceleration (PGA) ever recorded. The acceleration values 4022 and 1036 gal were observed at the surface and borehole accelerometers of IWTH25. To understand the cause of this extremely large acceleration, it is highly essential to obtain the detailed rupture process of Iwate–Miyagi earthquake. The present paper estimates the rupture model for this earthquake using the modified semi-empirical technique (MSET). The detailed analysis proposes one strong motion generation area (SMGA) in the rupture plane and nucleation point in the extreme western corner of the SMGA. Using this estimated source model, a satisfactory match is observed between the simulated and actual records. The quantitative analysis of these waveforms provides an almost 1:1 match for PGA values. Furthermore, the variation of these PGA values with epicentral distance shows similar attenuation rate. These results confirm the reliability of MSET and the estimated source model of this earthquake. To the best of our knowledge, this study is the first to model SMGAs in the rupture model using MSET and provides sufficiently reliable information which will be useful for seismic hazard prevention management.
Kumaon and Garhwal regions are the chief terrains of Uttarakhand Himalaya. The present article simulates the strong ground motion of the 2011 IndoNepal earthquake in the Kumaon region using modified semi empirical technique (MSET). Acceleration records at ten stations in the near field region have been simulated which validates well with actual records and therefore confirms the reliability of MSET. In addition, MSET has been used to simulate strong motion records of future scenario earthquakes (Mw 7.0 and Mw 8.0) in Kumaon region by assuming the earthquake location same as that of 2011 IndoNepal earthquake. Isoacceleration maps are also provided, which reveals more than 400 gal value of PGA at epicentral distances less than 25 kms for an earthquake of magnitude 8.0. The comparison of isoacceleration map of future scenario earthquake (Mw 7.0) in Kumaon region has been done with isoacceleration map of 1991 Uttarkashi earthquake (Mw 6.8) in Garhwal region which suggests distinct attenuation characteristics of these two regions.
