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On 25th April, 2015 a hazardous earthquake of moment magnitude 7.9 occurred in Nepal. Accelerographs were used to record the Nepal earthquake which is installed in the Kumaon region in the Himalayan state of Uttrakhand. The distance of the recorded stations in the Kumaon region from the epicenter of the earthquake is about 420–515 km. Modified semiempirical technique of modeling finite faults has been used in this paper to simulate strong earthquake at these stations. Source parameters of the Nepal aftershock have been also calculated using the Brune model in the present study which are used in the modeling of the Nepal main shock. The obtained value of the seismic moment and stress drop is 8.26 9 1025 dyn cm and 10.48 bar, respectively, for the aftershock from the Brune model .The simulated earthquake time series were compared with the observed records of the earthquake. The comparison of full waveform and its response spectra has been made to finalize the rupture parameters and its location. The rupture of the earthquake was propagated in the NE–SW direction from the hypocenter with the rupture velocity 3.0 km/s from a distance of 80 km from Kathmandu in NW direction at a depth of 12 km as per compared results.
We investigated ground response for Baku (Azerbaijan) from two earthquakes of magnitude M6.3 occurred in Caspian Sea (characterized as a near event) and M7.5 in Shamakhi (characterized as a remote extreme event). S-wave velocity with the average shear wave velocity over the topmost 30 m of soil is obtained by experimental method from the VP values measured for the soils. The downtown part of Baku city is characterized by low VS30 values (< 250 m/s), related to sand, water-saturated sand, gravel-pebble, and limestone with clay. High surface PGA of 240 gal for the M7.5 event and of about 190 gal for the M6.3 event, and hence a high ground motion amplification, is observed in the shoreline area, through downtown, in the north-west, and in the east parts of Baku city with soft clays, loamy sands, gravel, sediments.
The work presents an attempt of application of the horizontal-to-vertical spectral ratio (HVSR) method for estimating the local amplification of ground motion caused by mining seismic events in the Legnica Głogów Copper District. Amplifying properties of the surface layer are assessed from the ratio of amplitude spectra of the horizontal and vertical components of ground acceleration, recorded at the surface. The location of a local maximum of the ratio in the frequency band up to 8 Hz assigns the resonant frequency of the surface layer; the maximal value estimates the amplification factor at the measurement point. The spectral ratio was evaluated for 219 ground acceleration records from ten recording stations. The HVSR curves for induced seismicity turned out to be similar to the typical HVSR-s for natural earthquakes. Amplification factors estimated by the HVSR method were used to reduce the observed peak ground accelerations (PGA-s) to the bedrock. The reduction significantly improved an agreement beween the PGA values order and the order of epicentral distances. The obtained results suggest that the HVSR method can be successfully used to evaluate the local influence of the surface layer also for induced seismicity, in spite of the fact that in this case the conditions for application of the method essentially differ from the conditions met in natural seismicity.
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