Your search within this document for 'Earthquake' resulted in 14 matching pages.
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“... CrossMark ORIGINAL PAPER Determination of site effect and anelastic attenuation at Kathmandu, Nepal Himalaya region and its use in estimation of source parameters of 25 April 2015 Nepal earthquake Afw = 7.8 and its aftershocks including the 12 May 2015 A/„ = 7.3 event Parveen Kumar* 1 • A. Joshi2 • Sushil Kumar1 • Sandeep3 • Sohan Lal2 Received: 18 October 2016 / Accepted: 27 December 2017 / Published online: 29 January 2018 © Springer Science+Business Media B.V., part of Springer Nature 2018 Abstract The destructive A/w = 7.8 Nepal earthquake happened in Nepal Himalaya, 80 km NW of Kathmandu city on 25 April 2015. A number of aftershocks in which one of them is Mw = 7.3 which occurred on 12 May 2015 are observed around the Kathmandu city of Nepal. In this paper, strong motion data of Nepal earthquake and its eight aftershocks having magnitude range 5.3-7.3, recorded at Kathmandu station is used to determine site effects and attenuation factor. Kathmandu city, capital of Nepal, is situated...”
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“...3 41w = 7.8 earthquake and 1.40 X 1027 dyne cm, 44.7 bars, and 23.90 km, respectively, for the 12 May 2015 41w = 7.3 earthquake. Keywords Inversion • Quality factor • Spectra • Site effect 1 Introduction The epicenter of Nepal earthquake (Mw = 7.8) of 25 April 2015 is situated 80 km NW of Kathmandu city. The Kathmandu city, capital of Nepal, is situated in the Kathmandu valley which consists of a layer of sediments (Paudyal et al. 2013). The seismic amplification is increased due to soft deposits overlaid on the bedrock and cause more damage during the large earthquake, and this is called site effect (Kuo et al. 2012). Site effect is very significant term in the study of strong ground motion. The local site effect plays an important role in damage distribution during earthquakes. Throughout history, it is observed that destructions due to several earthquakes are influenced by local site effects (Luzon et al. 2004). The source spectrum has important information of earthquake source and wave...”
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“...Nat Hazards (2018) 91:1003-1023 1005 28.5° 27.5° 84.5° Fig. 1 Seismicity plot of Nepal Himalaya region illustrating seismicity around the Kathmandu. Grey circle shows the location of historical earthquakes occurred during 1971-2015 from USGS catalog. The tectonic is considered after Coleman and Hodges (1995) and MCT (Ni and Barazangi 1984; Seeber and Armbruster 1984), and it is observed from Fig. 1 that most of the historic earthquakes lie between the MBT and MCT. 3 Data A disastrous earthquake (Afw = 7.8) struck the Nepal region of central Himalaya on 25 April 2015. This main shock is followed by a number of aftershocks including 12 May 2015 41w = 7.3 event. The strong motion data of main shock of magnitude 7.8 (Afw) and its eight aftershocks having magnitude range 5.3-7.3 are recorded at Kathmandu station and used for the present work. This near-field data recorded in the hypocentral distance ranges from 21 to 85 km and as strong motion data recorded in desired passband without any clipping...”
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“...High Himalayan Metamorphic rocks O ▲ Lesser Himalayan metasedimentary series Main Central Thrust Main Boundary Thrust South Tibetan Detachment system Epicenter of main shock (Nepal earthquake) Epicenters of after shocks Recording Station Fig. 2 a Location of events and recording station with the elevation map of the present study area. Elevation data is taken from NOAA National Oceanic and Atmospheric Administration, b Geological map of the Kathmandu, Nepal Himalaya region (after Yin and Harrison 2000). (Figure modified after Shanker et al. 2011) SD(f) = 5A(f)/(2^/)2. (4) In this work, circular model proposed by Brune (1970) is considered to estimate earthquake source size, and stress drop as a circular model is quite enough to compute these parameters (Madariaga and Ruiz 2016). The source strength of an earthquake can be expressed by seismic moment (Af0). In the present work, long-term flat level (X20) and corner frequency (fc) obtained from ‘SD(f)’ are utilized to estimate Mo and are expressed...”
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“...for shear wave is considered as 0.63 (Atkinson and Boore 1995). Source radius (r0) is defined as the radius of circular crack of rupture. The expression of corner frequency and source radius, used in present work, is expressed as (Brune 1970, 1971): r0 = 2.34/?/2tt/c. (6) Stress drop (Ac) is another important source parameter of an earthquake. Stress drop is defined as difference of shear stress before and after the occurrence of event (Ruff 1999). The relation between source radius and stress drop is utilized for calculating the stress drop, and the expression is denoted below (Papageorgiou and Aki 1983): Aa = 7M„/I6A (7) The acceleration data of Nepal earthquake and its aftershocks is recorded at the Kathmandu station in Nepal. The Kathmandu region is situated in the valley known as Kathmandu valley, and the spectral data of these events are affected by the layer of sediments (Paudyal et al. 2013). Hence spectral data of present work are influenced by site effect and anelastic attenuation...”
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“...ground acceleration is associated usually with the arrival of S-wave (Hadley et al. 1982), so shear wave quality factor is estimated in this work. The inversion technique proposed by Joshi (2006a) and later modified by Joshi et al. (2012) and Kumar et al. (2015) is used to obtain site effect and gp(/). In this work, acceleration spectra A(f) is computed by following formula (Boore 1983 and Atkinson and Boore 1998): A(f) = CS(f)D(f) (8) where, ‘C’, ‘S(f)\ and are constant term at a station for an earthquake, acceleration source spectra, and diminution function which corresponds to anelastic attenuation and Springer...”
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“...the unknown parameter. Hence its natural logarithm makes this equation linearized. Now Eq. (8) is modified as: lnA(f) = InC + Zn(5(/,/c)) - nfR/ Qfflb - ln(R\ (11) By rearranging unknown and known terms and replacing the term referred to source acceleration spectrum S(f9fc) as (2rcf)2/(l + (flfy2) and by expanding on (1 + (flfp1) using Taylor series in order of/c, Eq. (11) is transformed in generalize form as: = InA^) - InC, - In [(2^/)2/ (l + (///c,)2)] + In (^). (12) The terms ‘f and denote earthquake and recording station number, respectively. The above equation can be represented in matrix form and the required parameters can be computed by solving this matrix using Newton’s method as described in Joshi et al. (2012) and Kumar et al. (2015). The corner frequency value is considered as one of the input parameter of the present inversion scheme so different solutions are obtained for several possibilities of ‘/c’. Final solution is obtained corresponding to minimum root-mean-square error...”
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“...1014 Nat Hazards (2018) 91:1003-1023 100^- c/5 2 4 6 8 10 Frequency (Hz) Fig. 7 Obtained site effects at Kathmandu station. The black lines represent the site effects obtained by inversion for NS and EW component. The grey portion represents the area between // + o and //-r» of site effect obtained by Lermo and Chavez-Garcia (1993). The terms and V describe the mean and standard deviation, respectively 5 Results and discussion The source parameters of 25 April 2015 Nepal earthquake (Afw = 7.8) and its aftershocks are determined from both North-South and East-West component of strong motion records. Time window, covering complete S phase, is used to estimate various source parameters. This time window is cosine tapered and has 10% tapering for both ends (Sharma and Wason 1994). The FFT algorithm is used to obtain spectrum of this series and obtained spectrum is corrected for site effect and anelastic attenuation term. The site effects and shear wave quality factor are determined from the...”
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“...average values of NS and EW component. Source displacement spectra of Nepal earthquake and its aftershocks are compared with Brune’s (1970) theoretical spectra for both NS and EW component and shown in Figs. 10 and 11, respectively. The obtained values of seismic moment, stress drop, and source radius vary from 1.11 x 1024 to 5.96 X 1027 dyne cm, 9.5 to 48.7 bars, and 3.7 to 37.75 km, respectively. The various source parameters for both horizontal components of all the events are given in Table 3. Figure 12 represents the plot of hypocentral distance (R) versus seismic moment (Af0). The average value of seismic moment, source radius and stress drop obtained from both North-South and East-West component is 5.96 X 1027 dyne cm, 37.75 km and 48.7 bars, respectively, for the 25 April 2015 41w = 7.8 Nepal earthquake and 1.40 X 1027 dyne cm, 23.90 km and 44.7 bars, respectively, for the 12 May 2015 41w = 7.3 earthquake. The rupture area is calculated by using the obtained value of source radius...”
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“...particular earthquake, respectively. The terms 'a' and ‘Z?’ denote the coefficient having value, a = - 3.49 and b = 0.91 (Wells and Coppersmith (1994)). The standard errors suggested by Wells and Coppersmith (1994) for the terms 'a' and ‘Z?’ are ± 0.16 and ± 0.03, respectively. The rupture area values calculated by the obtained source radius and empirical relation are given in Table 4. It is observed that the rupture area values calculated in present work lie well within the range of rupture area values computed by empirical relation. The stress drop values are calculated by many workers in the different part of Himalaya region by using different earthquakes. The stress drop values in the different part of Himalayan region are estimated as 34 ± 3.79 bars for Nepal earthquake (Afw = 7.8) of 2015 (Mitra et al. 2015); 0.1 to 61.7 bars for the Nubra region, Leh and Ladakh Himalaya, for the earthquakes of magnitude range 2.7-5.0 (Parshad et al., 2014); 59.2 ± 8.8 bar for Sikkim earthquake (Afw =...”
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“...r AF2 ff4 7 Afr —I 1 1 20 40 60 80 Hypocentral Distance (km) Fig. 12 Plot of seismic moment values correspond to different hypocenral distance for all events used in present work of 2011 (Joshi et al. 2014); 0.14-38.59 bars for the Arunachal Himalaya for the events of magnitude range 0.9-3.0 (Kumar et al. 2013); 0.08-28.4 bars for the Jammu and Kashmir Himalaya region for the earthquakes of magnitude range 1.7-3.8 (Bhat et al. 2013); 98 bars for Chamoli earthquake (Ms = 6.6) of 1999 (Joshi 2006b); 53 bars for Uttarkashi earthquake (Ms = 7.0) of 1991 (Kumar et al. 2005). Stress drop values computed in the present work varies from 9.5 to 48.7 bars for all the events used in this work. The obtained stress drop values for different earthquakes show close resemblance with the available stress drop values in the different part of the Himalaya region. Furthermore, seismic moment values are calculated by using empirical formula proposed by Hanks and Kanamori (1979) and Wells and Coppersmith...”
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“...http://earthquake.usgs.gov is thankfully acknowledged. References Aki K (1967) Scaling law of seismic spectrum. J Geophys Res 72:1217-1231 Aki K, Richards PG (1980) Quantitative Seismology: Theory and Methods. W. H. Freeman and Co., New York Aki K, Richards PG (2002) Quantitative seismology, 2nd edn. University Science Books, Sausalito Atkinson GM, Boore DM (1995) Ground-motion relation for eastern North America. Bull Seismol Soc Am 85:17-30 Atkinson GM, Boore DM (1998) Evaluation of models for earthquake source spectra in eastern North America. Bull Seismol Soc Am 88:917-934 Bhat GM, Pandita SK, Singh Y, Sharma S (2013) Estimation of source parameters of local earthquakes in Jammu and Kashmir, India. Int J Sci Res 3(2): 1-5 Bhattacharya AR (2008) Basement rocks of the Kumaun-Garhwal himalaya: implications for Himalayan tectonics. J Earth Sci India 1(1): 1-10 Boore DM (1983) Stochastic simulation of high frequency ground motion based on seismological models of radiated Spectra. Bull Seismol...”
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“...Seismol Soc Am 96:2165-2180 Joshi A (2006b) Analysis of strong motion data of the Uttarkashi earthquake of 20th October 1991 and the Chamoli earthquake of 28th March 1999 for determining the mid crustal Q value and source parameters. J Earthq Technol 43:11-29 Joshi A, Kumar P, Mohanty M, Bansal AR, Dimri VP, Chadha RK (2012) Determination of Qp(f) at different places of Kumaon Himalaya from the inversion of spectral acceleration data. Pure appl Geophys 169:1821-1845 Joshi A, Kumar P, Arora S (2014) Use of site amplification and anelastic attenuation for the determination of source parameters of the Sikkim earthquake of September 18, 2011, using far-field strong-motion data. Nat Hazards 70:217-235 Katel TP, Upreti BN, Pokharel GS (1996) Engineering properties of fine grained soils of Kathmandu Valley Nepal. J Nepal Geol Soc 13:121-138 Ko YT, Kuo BY, Hung SH (2012) Robust determination of earthquake source parameters and mantle attenuation. J Geophys Res 117:B04304. https://doi.org/10.1029...”
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“...Nat Hazards (2018) 91:1003-1023 1023 Mittal H, Kumar A (2015) Stochastic finite fault modeling of Mw 5.4 earthquake along Uttarakhand-Nepal border. Nat Hazards 75(2):1145-1166 Mittal H, Kumar A, Kamal (2013) Ground motion estimation in Delhi from postulated regional and local earthquakes. J Seismol 17(2):593-605 Mittal H, Wu YM, Chen DY, Chao WA (2016) Stochastic finite modelling of ground motion for March 5th 2012 Mw 4.6 earthquake and scenario greater magnitude earthquake in the proximity of Delhi. Nat Hazards 82(2): 1123-1146 Nath SK, Vyas M, Pal I, Singh AK, Mukherjee S, Sengupta P (2005) Spectral attenuation models in the Sikkim Himalaya from the observed and simulated strong motion events in the region. Curr Sci 88(2):295-303 Ni J, Barazangi M (1984) Seismotectonics of the Himalayan Collision Zone: geometry of the Underthrusting Indian Plate beneath the Himalaya. J Geophys Res 89:1147-1163 Papageorgiou A, Aki K(1983)A specific barrier model for the quantitative description of inh...”