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6 A sample strong-motion (GeoSig) record of a Mw 6.5 earthquake from Hindukush region recorded at the Keylong station (epicentral distance 717 km) on September 17, 2010
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Three chief tectonic sub-regions of India (GSI, 2000) are the mighty Himalayas along the north, the plains of the Ganges and other rivers, and the peninsula. The Himalayas consist primarily of sediments accumulated over long geological time in the Tethys. A number of efforts are being made to study seismic hazard from earthquakes originating from H...
Citations
... India India is one of the countries that face a seismic threat from different regions, namely north and the northeast Himalayas, Kuchchh region in Gujarat, and Nicobar Island in the southeast part (Kumar and Mittal 2018). The construction of a single EEW for the whole country is not feasible. ...
Several natural hazards, including earthquakes, may trigger disasters and the presence of disaster drivers further lead to the massive loss of life and property, every year around the world. The earthquakes are unavoidable, as exact earthquake prediction in terms of date, and time is difficult. However, with the advancement in technology, earthquake early warning (EEW) has emerged as a life-saving guard in many earthquake-prone countries. Unlike other warning systems (where hours of warning are possible), only a few seconds of warning is possible in the EEW system, but this warning may be very helpful in saving human lives by taking the proper action. The concept of EEW relies on using the initial few seconds of information from nearby instruments, performing basic calculations, and issuing the warning to the farther areas. A dense network or enough network coverage is the backbone of an EEW system. Because of insufficient station coverage, the estimated earthquake location is error-prone, which in turn may cause problems for EEW in terms of estimating strong shaking for the affected areas. Seismic instrumentation for EEW has improved significantly in the last few years considering the station coverage, data quality, and related applications. Many countries including the USA, Mexico, Japan, Taiwan, and South Korea have developed EEW systems and are issuing a warning to the public and authorities. Several other countries, namely China, Turkey, Italy, and India are in process of developing and testing the EEW system. This article discusses the challenges and future EEW systems developed around the world along with different parameters used for EEW.
Article Highlights
This article aims to provide a comprehensive review related to the development
The explicit emphasis is on the scientific development of EEW parameters
The challenges and future scopes for the effective implementation of EEWS are discussed in terms of the correct location, the magnitude estimation, the region-specific use of ground motion prediction equations, communication technologies, and general public awareness
... Abundant low-level seismicity and the awareness of earthquake exposure of NCR has led to a steady increase in the seismic and accelerographic instrumentation in and near NCR during last two decades (Bhattacharya and Dattatrayam 2000;Kumar and Mittal Shukla et al. 2018;Bansal et al. 2021a). Consequently, our knowledge of the seismicity of the region has improved, revealing a prolific activity of small earthquakes. ...
We study source parameters of 10 local earthquakes (2.7 ≤ \(M_{w}\) ≤ 4.5) that have occurred in the National Capital Region (NCR) since 2001 and the ground motions produced by these events. Moment rate spectra of the earthquakes retrieved from the recordings at hard sites after applying corrections for geometrical spreading (1/R, R ≤ 100 km), anelastic attenuation (Q = 253f0.8) and cutoff frequency (fm = 35 Hz) are reasonably well fit by the Brune ω2-source model with stress drop ranging between 0.9 and 13 MPa. Neglecting the outlier low-stress drop value, the average stress drop is 6 MPa. We apply a modified standard spectral ratio technique to estimate site effect at 38 soft sites in the NCR as well as the geometrical mean site effect with respect to a reference hard site. Application of the stochastic method, with source characterized by the Brune ω2- model with stress drop of 6 MPa and the mean site effect for soft sites, yields peak horizontal ground acceleration and velocity curves that are in good agreement with the observed values. These results provide the parameters needed for the application of the stochastic method to predict ground motions at hard and soft sites in the NCR during postulated \(M_{w}\) ≤ 5.5 earthquakes.
... Two types of instruments (Geosig and Kinemetrics) were used to collect these data in the Delhi region. All the instruments having higher dynamic range are installed in free-field, and recording is done using a higher sampling frequency, i.e. 200 samples per second (Mittal et al. 2006;Kumar and Mittal 2018). The used data consist of 19 earthquakes having a magnitude range of 2.5-4.9 and a depth between 5 and 22 km. ...
The recorded strong motion data in the Delhi region provide an excellent opportunity to study high-frequency decay parameter, kappa (κ) for the National Capital (Delhi) region and to further understand its implications to study the site effects characterized by different stations within the vicinity of the study region. The kappa values are estimated at 30 locations from 99 accelerograms of 19 earthquakes recorded in the Delhi region and are found to vary from place to place depending upon the controlling parameters, primarily the site characterization. The estimated average values of ‘κ’ lie in the range 0.0118–0.0537 s for the various locations of the region depending upon the source, path, and site characteristics of earthquakes considered in the present study. The distance dependence is found insignificant, while there is a scatter in the variation of κ values with that of magnitude which indicates that κ is more related to the site characteristic for the entire Delhi region which in turn reveals the fact of the basic criterion of the κ parameter. To affirm the total attenuation on the instruments, the site effects demonstrate the behavior of amplification to the geological exposure. It has been found that the various sites under consideration for the study area amplify between 0.6 and 7.0 Hz predominant frequency (\({f}_{\mathrm{peak}}\)) and agree with the geological arrangements of the region. Based on the present study, the most vulnerable areas are the northeastern region of Delhi which lies in proximity to the flood plains of Yamuna river and alluvial deposits of younger origins of the foreland basin along with the southwestern part of Delhi capital which is comprised of the water-saturated alluvial deposits. The estimated ‘κ’ values are found to be correlated with those of the estimated site amplifications and are useful in strong ground motions simulation for the proper evaluation of seismic hazard to build a seismic risk resilient society.
... The fidelity of the technique, used in the present study for the NCR, has been tested by modeling the observed accelerograms of the earthquake (M 4.7) that occurred on November 25, 2007, at the Sohna fault near Bahadurgarh, Haryana-Delhi border, and was recorded by strong motion instrumentation network (Kumar and Mittal 2018). This network generated data related to various earthquakes occurring in different parts of the country (Mittal et al. 2006). ...
Delhi, National Capital Region (NCR) of India, falls in the seismic Zone IV (Zone factor 0.24) on the seismic zoning map prepared by the Bureau of Indian Standards (BIS), and this region may experience devastating intensities in case of plausible moderate to the major earthquake in the vicinity. The strategic geological, geomorphological, and geographic characteristics make this seat of administrative power more vulnerable toward the earthquake disaster right from the ancient periods. Therefore, we study the impact of the M 6.0 earthquake sourced at Sohna fault in the neighborhood of the capital region by generating synthetic accelerograms through semiempirical envelop technique. The observed accelerograms of November 25, 2007 (Mw 4.7) earthquake have been modeled to utilize the reliability of the semiempirical approach. To analyze the actual scenario, the ground motions at the surface have been generated after the incorporation of the site effects because different soil conditions of NCR fascinate different degrees of damage in case of a destructive earthquake. As a result, the obtained peak ground acceleration (PGA) varies between 100 and 600 cm/s2, and some of the sites exhibit even higher PGA values being situated on the sediments of river-oriented plain areas and proximity of the source. The spatial distribution of estimated values of PGA and spectral accelerations at different periods show that sites in NCR like Delhi (600 cm/s2), Sonipat (633 cm/s2), Gurgaon (461 cm/s2), and Faridabad (300 cm/s2) exhibit high to severe seismic hazard in case of M 6.0 at Sohna fault and it is suggested that a population of about 4.78 million along with the infrastructure of this region is exposed to high risk. The estimated seismic exposure of the population is important to utilize the resources properly before the destructive earthquake incidence. The hazard maps for PGA and different structural periods in the NCR region reveal the level of seismic hazard and risk of the study region. These hazard maps are very helpful for administrators, stakeholders, and civil engineers to construct earthquake-resistant structures to minimize the risk generated by the future impending earthquakes. The exponential growth of the buildings, industries, businesses, etc., attracts the attention of urban area planners because of high seismic risk due to the damaging earthquakes, and its severity must be understood to save the life and property to mitigate the natural disaster like an earthquake by proper disaster mitigation plans, especially in the metropolitan cities like Delhi NCR.
... This instrumentation consisting of 300 instruments was installed in seismic zone IV and V in the Himalayan belt, as well as, some of the thickly populated cities falling in zone III. All of these instruments have a wide dynamic range (108 dB), to provide precise records in the near field (Kumar and Mittal 2018;Mittal et al. 2006). The instruments are equipped with external GPS for time correction. ...
... rang Faultt have plotted along with major faults like Main Boundary Thrust (MBT) and Min Central Thrust (MCT). The stations recording these earthquakes are shown as triangles. The two regions used for Q estimation are shown as region 1 with a red outline and 2 with blue outline respectively. The earthquake data is collected from https://pesmos.com/(Kumar and Mittal 2018). ...
This study aims to estimate attenuation characteristics of the central Himalayan region of India concerning various strong-motion parameters such as Kappa value (κ) and site effects. We have tried to elaborate on the regional structural heterogeneities and their implications towards the seismic hazard assessment of the study region. A total of 81 earthquakes recorded at 50 stations situated in the central Himalayan region of India are used for the purpose. The particular focus is kept on Kappa value, which shows variability from 0.03 s to 0.095 s, inferring the higher values obtained in plains with deep sediment accumulations proving high-frequency energy dissipation and stiff-soil/rocky sites exhibit comparatively limited attenuation accordingly. To substantiate these results various attenuation parameters such as coda wave quality factor (Qc), intrinsic attenuation parameter (Qi), and scattering attenuation parameter (Qs), have been estimated for two regions in the central seismic gap Himalayan region of India employing the single backscattering model and Wennerberg formulation. The estimated values of Qc, Qi, and Qs are found to be highly dependent on frequency in the frequency range 1.5–24 Hz for both the regions. The average frequency-dependent relationships (Q=Q0fη) estimated for both regions are Qc=158f1.18 and Qc=194f1.2, respectively. The low value of Q0 shows that the region is highly heterogeneous while the higher value of η indicates higher seismicity in the area. It is also found that intrinsic attenuation is predominant over the scattering attenuation, envisaging the behavior of the wave attenuation through the absorption within the granitic layer at shallow depths. At lower frequencies, Qc values are found close to Qs values, which is in agreement with the theoretical measurements suggesting the presence of complex crustal heterogeneities beneath the region affecting the propagation of seismic waves experiencing considerable decay of energy through scattering. To confirm the aggregate attenuation on the stations, the site characteristics are also determined for examining the behavior of the amplification as the ground motion is comprised of the combined effect of the source, path, and site. The sites are amplified at a predominant frequency ( fpeak ) in between 1.5 to 10 Hz for the central Himalayan region. The different attenuation and amplification parameters like kappa, Q, and site effects can be utilized for detailed seismic hazard analysis (based on ground motion prediction equations) of the area as this region is of great importance from a socio-economic point of view.
... The recorded strong motion data of 37 events in NEI and the surrounding area from 2009 to 2016 has been used for the present work ( Figure 1). These events are recorded at 25 strong-motion stations operated by the Indian Institute of Technology (IIT)-Roorkee (Kumar and Mittal 2018;Mittal et al. 2006); in the present time operated by National Centre for Seismology (NCS), New Delhi as shown in Figure 2. This network has recorded a number of earthquakes since its deployment and recorded data has been used by various researchers for different studies (e. g. ...
Site effect estimation using recorded ground motion is an effective approach to assess the seismic hazard of a region. Keeping the same thing in mind, an endeavor is being made to study the local site effects at different locations in the North East region of India through analysis of recorded strong ground motion data provided by Indian strong motion network. The data recorded at 25 sites from 37 earthquakes with a magnitude range ML 4.0–6.9 have been utilized. The estimated predominant frequencies ( fpeak) using horizontal to the vertical spectral ratio (HVSR) is well observed for various sites placed in various geological formations like the Precambrian, Tertiary and Quaternary Consequently, the pseudo velocity response (PSV) for 5% critical damping is estimated and compared with the regional geological formations, especially in the Brahmaputra Valley region. It is further noticed that the HVSR, as well as PSV, show a noticeable correlation according to the geological set up of the region for most of the sites, giving a clear idea about the site effect evaluation. Analyzed strong motion data also show the effect of non-linearity, which is an important parameter as it explains the inelastic behavior of the soil causing a reduced or non-linear amplification. Since some of the sites used in present work do not correlate with geology, the sites used for HVSR estimation are used to classify them according to the classical approach employing fpeak. All the sites are classified in four different classes namely A, B, C, and D based on shear wave velocity in the upper 30 m. The outcome of the present study is being shown in the form of contour maps for fpeak and site amplification for various types of buildings in order to assess the seismic hazard and risk mitigation.
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.
The proximity of Delhi and the surrounding region to the active faults along with its geographical settings is a subject of discussion to comprehend the seismic resilience of the capital region of India. The region may be affected by the far-field earthquakes from the Himalayas as well as the near-field earthquakes associated with the local seismic activity. Considering the ordinary settings of this region, the present study is an insight to differentiate the damage potential of ground motion associated with near and far-field conditions to further see their consequences to understand the comprehensive seismic hazard of the region. The acceleration and velocity response analysis of recorded strong ground motions from far-field and near-field earthquakes exhibit a clear distinct behavior in the form of amplification and corresponding predominant period. The comparison of estimated normalized spectral accelerations with that of the seismic design code of the Bureau of Indian Standards (BIS), shows that the current Indian building design code is within the structural limits proposed for the seismic forces of long periods, however, exceeded amplitude of the normalized Spectral Acceleration for far-field earthquakes may be attributed towards the damage potential for the high rise buildings in the capital region of India. On the other hand, near-field earthquakes do not meet the criteria with the design code of BIS at lower periods from 0.02s to 0.09s along with the amplified Spectral acceleration. It also suggests that the structural heterogeneities within the subsurface of Delhi and the surrounding region have a strong bearing in contributing to the impact of seismic waves from near-field earthquakes producing short-period waves that may be disastrous for low-rise buildings. Based on the results, the study region affected by the distinct seismicity patterns is important to understand the shaking behavior of the different kinds of infrastructures/buildings in case of near-field and far-field earthquakes to appropriately utilize the information for constructing new buildings and strengthening the existing infrastructures in Delhi and the surrounding region of India.
