is operating broadband seismic stations in different parts of India. The stations are equipped wi... more is operating broadband seismic stations in different parts of India. The stations are equipped with latest generation seismometers with high sensitivity like CMG-40T, CMG-3ESP. The data acquisition systems have high dynamic range (144dB), achieved by a 24-bit digitizer and recorded at 100 samples per second. This earthquake was recorded at Hyderabad. Cuddapah, Kothapudeh. Naldurg in southern peninsular India. at stat~ons of Tezpur selsmlc network in Northeast India and at stations of Koyna seismic network in Western India Surface waves are clipped at most of the stations (except at Kothagudem and Cuddapah where the seismometer is CMG-40T), which dld not allow us to estimate earthquake parameters uslng surface waves. The nearest NGRI seismic station to record this event is at an epicentral distance of about 2230 km. Waveforms recorded at NGRI se~smic stations are shown in Fig. 1.
We report estimation of site response in the form of fundamental frequency. Towards this objectiv... more We report estimation of site response in the form of fundamental frequency. Towards this objective, we deploy widely established receiver function technique. Taking locally recorded events as inputs, we implement this technique to estimate resonance frequency in three receiver sites, characterized by varying lithology underneath. It is observed that resonance frequencies varies from 3 to 7 Hz, which is also confirmed by our previous studies of estimates from ambient noise recordings with reference to identical sites. Variation of frequency implies existence of heterogeneity in the study area.
We report here a preliminary investigation on site effects in a highly populated zone of academic... more We report here a preliminary investigation on site effects in a highly populated zone of academic importance. The study area is mostly characterized by its alluvial sediments. Due to its rapid deve...
Estimation of spatial variation of site response is one of the prime objectives of microzonation ... more Estimation of spatial variation of site response is one of the prime objectives of microzonation studies. Several literatures outlined the paramount significance of site dependent factor which largely impact the extent of damage in certain pocket areas pertaining to local geology.1–7 Even the shaking of man–made structures also gets affected by the spatial variation of site effects. The site effects can be parameterized by factors like resonance frequency, amplification factor which have direct impact on semi–resonance or resonance of certain building types, and thereby causing distortions or failures of constructions. In order to compute site response, there are adoptions of various methodologies.8–11 HVSR or receiver function technique has been widely regarded as one of the most powerful methods available to seismologist for acquiring a reliable estimate of site response.
Geophysical Lab, Department of Physics, Tezpur University, Tezpur-784028, Assam Corresponding aut... more Geophysical Lab, Department of Physics, Tezpur University, Tezpur-784028, Assam Corresponding author: [email protected] Kopili fault has been experiencing higher seismic and tectonic activity ([1], [2]) during the recent years. These kinds of active tectonics can be inspected by examining coda-wave attenuation and its dependence with frequency. Here, we report spatial variation of coda attenuation of this region. The obtained results reveal that there is velocity anomaly at depth 210-220 km as there arises sharp changes in attenuation coefficient (γ) and frequency parameter (n) which are supported by available data reported by other researchers for this region.
Witch-hunting practice has been traditionally a part of belief in rural India. Like other parts o... more Witch-hunting practice has been traditionally a part of belief in rural India. Like other parts of India, Assam also witnesses this atrocious practice at an alarming stage. 210 cases of witch-hunting have been occurred in Assam during the period 1989-2019, which is a severe quandary to the advancing society. Killings in the name of witch-hunting also violates human rights as well as women rights as majority of the victim branded as ‘witch’ are women. This paper tries to highlight witch hunting practice, witch-trials and witch-hunting phenomena globally, nationally and primarily in the context of Assam. It also elaborates the legal safety afforded by the state of Assam in general. This paper accomplishes with an assessment of the efficacy of the legal instruments implemented for protection of ‘witch-hunting’. The paper attempts to identify the causes responsible for witch-hunting with some practical solution to tackle this social menace.
International Journal of Geotechnical Earthquake Engineering
Attenuation study of a province is considered as a basic quantity for seismic hazard assessment. ... more Attenuation study of a province is considered as a basic quantity for seismic hazard assessment. It has already been established that the study of two physical processes, namely the seismic sources and propagation of the waves, is essential for seismic-hazard mapping. Additionally, attenuation plays an important role towards scaling seismic hazard. Accordingly, a computational tool entitled CodaQback is presented. Based on back scattering model, this versatile software is equipped with user-friendly graphical user interface. It also allows quick picking of phases for computing coda attenuation parameter. All outputs after each execution step in CodaQback are efficiently exported step-wise into a separate folder in Excel and text formats. To validate the computing tool, it is tested in real data analysis and there is found to be good matching of computed values with already established ones. It is envisioned that this package will enable user to derive quick and reliable estimation o...
We comprehensively analyze attenuation factor in Kopili region and its neighboring area. Correspo... more We comprehensively analyze attenuation factor in Kopili region and its neighboring area. Corresponding to influence of frequency on attenuation, Q P and Q S are estimated from direct P and S waves. The results establishes higher values of Q for S waves (Q S =(101±4)f(1.4±0.05)) than for P waves (Q P =(45±3)f(1.3±0.07))in the 1.5-12 Hz frequency band. It is seen that our findings agree with other published results on tectonically active regions that is characterized by high degree of heterogeneity. Hence, it can be useful for further studies in ground motion prediction in Kopili region. The low value of quality factors corresponding to P and S waves refers to seismically actives areas with complex heterogeneity. The estimated value of Q S /Q P and their subsequent association with frequency affirm the dominance of scattering as a major contribution to diminution of seismic amplitudes. This is further corroborated by local geological settings.
We evaluated the body wave attenuation parameter in Kopili region of northeast India. Using the m... more We evaluated the body wave attenuation parameter in Kopili region of northeast India. Using the modified algorithm of coda normalization method, we delineated frequency-dependent attenuation for both P and S waves. Taking more than 300 seismograms as input, we comprehensively studied microearthquake spectra in the frequency range of 1.5 to 12 Hz. The estimated values of −1 and −1 show strong frequency dependence. Based on this, we formulated empirical relationships corresponding to −1 and −1 for the study region. The relationships emerge to be −1 = (23.8 ± 6) × 10 −3 (−1.2±0.008) and −1 = (10.2 ± 2) × 10 −3 (−1.3±0.02) , respectively. The ratio −1 −1 ⁄ is found to be larger than unity for the entire frequency band which implies profound seismic activity and macroscale heterogeneity prevailing in the region. The study may act as the building block towards determination of source parameter and hazard related studies in the region.
Microearthquake spectra from the Kopili region, one of the seismic prone areas of northeast India... more Microearthquake spectra from the Kopili region, one of the seismic prone areas of northeast India, are examined to observe the effect of attenuation on these spectra. The spectral ratio method is utilized in order to estimate Q values for both P and S waves in the subsurface layer wherein the ratio of spectral amplitudes at lower and higher frequencies are taken into consideration for six stations at varying epicentral distances. Average values of Q p and Q s are computed to be ∼481±36 and 966±98, respectively. Q s /Q p having a value greater than 1 is contemplated in major parts of Kopili and the neighboring area, which can be ascribed to underlying sediment deposits. The estimates of attenuation parameters are well substantiated by site geology. The values obtained in this study are in good conformity with the worldwide average. The estimates will help in seismic hazard estimation of this seismically active area.
is operating broadband seismic stations in different parts of India. The stations are equipped wi... more is operating broadband seismic stations in different parts of India. The stations are equipped with latest generation seismometers with high sensitivity like CMG-40T, CMG-3ESP. The data acquisition systems have high dynamic range (144dB), achieved by a 24-bit digitizer and recorded at 100 samples per second. This earthquake was recorded at Hyderabad. Cuddapah, Kothapudeh. Naldurg in southern peninsular India. at stat~ons of Tezpur selsmlc network in Northeast India and at stations of Koyna seismic network in Western India Surface waves are clipped at most of the stations (except at Kothagudem and Cuddapah where the seismometer is CMG-40T), which dld not allow us to estimate earthquake parameters uslng surface waves. The nearest NGRI seismic station to record this event is at an epicentral distance of about 2230 km. Waveforms recorded at NGRI se~smic stations are shown in Fig. 1.
We report estimation of site response in the form of fundamental frequency. Towards this objectiv... more We report estimation of site response in the form of fundamental frequency. Towards this objective, we deploy widely established receiver function technique. Taking locally recorded events as inputs, we implement this technique to estimate resonance frequency in three receiver sites, characterized by varying lithology underneath. It is observed that resonance frequencies varies from 3 to 7 Hz, which is also confirmed by our previous studies of estimates from ambient noise recordings with reference to identical sites. Variation of frequency implies existence of heterogeneity in the study area.
We report here a preliminary investigation on site effects in a highly populated zone of academic... more We report here a preliminary investigation on site effects in a highly populated zone of academic importance. The study area is mostly characterized by its alluvial sediments. Due to its rapid deve...
Estimation of spatial variation of site response is one of the prime objectives of microzonation ... more Estimation of spatial variation of site response is one of the prime objectives of microzonation studies. Several literatures outlined the paramount significance of site dependent factor which largely impact the extent of damage in certain pocket areas pertaining to local geology.1–7 Even the shaking of man–made structures also gets affected by the spatial variation of site effects. The site effects can be parameterized by factors like resonance frequency, amplification factor which have direct impact on semi–resonance or resonance of certain building types, and thereby causing distortions or failures of constructions. In order to compute site response, there are adoptions of various methodologies.8–11 HVSR or receiver function technique has been widely regarded as one of the most powerful methods available to seismologist for acquiring a reliable estimate of site response.
Geophysical Lab, Department of Physics, Tezpur University, Tezpur-784028, Assam Corresponding aut... more Geophysical Lab, Department of Physics, Tezpur University, Tezpur-784028, Assam Corresponding author: [email protected] Kopili fault has been experiencing higher seismic and tectonic activity ([1], [2]) during the recent years. These kinds of active tectonics can be inspected by examining coda-wave attenuation and its dependence with frequency. Here, we report spatial variation of coda attenuation of this region. The obtained results reveal that there is velocity anomaly at depth 210-220 km as there arises sharp changes in attenuation coefficient (γ) and frequency parameter (n) which are supported by available data reported by other researchers for this region.
Witch-hunting practice has been traditionally a part of belief in rural India. Like other parts o... more Witch-hunting practice has been traditionally a part of belief in rural India. Like other parts of India, Assam also witnesses this atrocious practice at an alarming stage. 210 cases of witch-hunting have been occurred in Assam during the period 1989-2019, which is a severe quandary to the advancing society. Killings in the name of witch-hunting also violates human rights as well as women rights as majority of the victim branded as ‘witch’ are women. This paper tries to highlight witch hunting practice, witch-trials and witch-hunting phenomena globally, nationally and primarily in the context of Assam. It also elaborates the legal safety afforded by the state of Assam in general. This paper accomplishes with an assessment of the efficacy of the legal instruments implemented for protection of ‘witch-hunting’. The paper attempts to identify the causes responsible for witch-hunting with some practical solution to tackle this social menace.
International Journal of Geotechnical Earthquake Engineering
Attenuation study of a province is considered as a basic quantity for seismic hazard assessment. ... more Attenuation study of a province is considered as a basic quantity for seismic hazard assessment. It has already been established that the study of two physical processes, namely the seismic sources and propagation of the waves, is essential for seismic-hazard mapping. Additionally, attenuation plays an important role towards scaling seismic hazard. Accordingly, a computational tool entitled CodaQback is presented. Based on back scattering model, this versatile software is equipped with user-friendly graphical user interface. It also allows quick picking of phases for computing coda attenuation parameter. All outputs after each execution step in CodaQback are efficiently exported step-wise into a separate folder in Excel and text formats. To validate the computing tool, it is tested in real data analysis and there is found to be good matching of computed values with already established ones. It is envisioned that this package will enable user to derive quick and reliable estimation o...
We comprehensively analyze attenuation factor in Kopili region and its neighboring area. Correspo... more We comprehensively analyze attenuation factor in Kopili region and its neighboring area. Corresponding to influence of frequency on attenuation, Q P and Q S are estimated from direct P and S waves. The results establishes higher values of Q for S waves (Q S =(101±4)f(1.4±0.05)) than for P waves (Q P =(45±3)f(1.3±0.07))in the 1.5-12 Hz frequency band. It is seen that our findings agree with other published results on tectonically active regions that is characterized by high degree of heterogeneity. Hence, it can be useful for further studies in ground motion prediction in Kopili region. The low value of quality factors corresponding to P and S waves refers to seismically actives areas with complex heterogeneity. The estimated value of Q S /Q P and their subsequent association with frequency affirm the dominance of scattering as a major contribution to diminution of seismic amplitudes. This is further corroborated by local geological settings.
We evaluated the body wave attenuation parameter in Kopili region of northeast India. Using the m... more We evaluated the body wave attenuation parameter in Kopili region of northeast India. Using the modified algorithm of coda normalization method, we delineated frequency-dependent attenuation for both P and S waves. Taking more than 300 seismograms as input, we comprehensively studied microearthquake spectra in the frequency range of 1.5 to 12 Hz. The estimated values of −1 and −1 show strong frequency dependence. Based on this, we formulated empirical relationships corresponding to −1 and −1 for the study region. The relationships emerge to be −1 = (23.8 ± 6) × 10 −3 (−1.2±0.008) and −1 = (10.2 ± 2) × 10 −3 (−1.3±0.02) , respectively. The ratio −1 −1 ⁄ is found to be larger than unity for the entire frequency band which implies profound seismic activity and macroscale heterogeneity prevailing in the region. The study may act as the building block towards determination of source parameter and hazard related studies in the region.
Microearthquake spectra from the Kopili region, one of the seismic prone areas of northeast India... more Microearthquake spectra from the Kopili region, one of the seismic prone areas of northeast India, are examined to observe the effect of attenuation on these spectra. The spectral ratio method is utilized in order to estimate Q values for both P and S waves in the subsurface layer wherein the ratio of spectral amplitudes at lower and higher frequencies are taken into consideration for six stations at varying epicentral distances. Average values of Q p and Q s are computed to be ∼481±36 and 966±98, respectively. Q s /Q p having a value greater than 1 is contemplated in major parts of Kopili and the neighboring area, which can be ascribed to underlying sediment deposits. The estimates of attenuation parameters are well substantiated by site geology. The values obtained in this study are in good conformity with the worldwide average. The estimates will help in seismic hazard estimation of this seismically active area.
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