Sayed S. R. Moustafa

Selection of Ground Motion Prediction Equations for Seismic Hazard Analysis of Peninsular India

Seismic hazard analysis provides an estimation of seismic hazard parameters like peak ground acceleration (PGA) or spectral acceleration (SA) for different periods. The extent of ground shaking and the hazard values at a particular region are estimated using ground-motion prediction equations (GMPEs)/attenuation equations. There are several GMPEs applicable for the region to estimate the PGA and SA values. These equations may result in higher or lower PGA and SA values than the region specific reported values, which are based on the parameters involved in the development of GMPEs. In this study, an attempt has been made to identify the best GMPEs for various parts of Peninsular India (PI) by performing an “efficacy test,” which make use of the average log likelihood value (LLH). Various intraplate earthquakes such as Coimbatore earthquake, Satpura earthquake, Anjar earthquake, Koyna earthquake, Bhadrachalam earthquake, Broach earthquake, Shimoga earthquake, Killari earthquake, Jabalpur earthquake, Pala earthquake, Kottayam earthquake, and Bhuj earthquake have been considered for the same. Macroseismic intensity maps of these earthquakes have been digitalized and European Macroseismic Scale (EMS) values at the surface have been synthesized. PGA value determined from each GMPE for known magnitude and hypocentral distances are then converted to EMS values. These calculated EMS values have been used to estimate LLH values which are further used to compute Data Support Index (DSI), rank and weights corresponding to a particular GMPE. Conventionally, LLH values are estimated for the entire distance range and GMPEs are ranked accordingly, but in this study, the LLH is calculated for the distance segments of 0-200 km and 200 km to maximum damaged distance in the region based on Isoseismal maps. If the maximum damaged distance is less than 200 km, a distance segment up to 200 km is adopted. Comparison between the rankings of the GMPEs in segments 0–200 km and 200–maximum damage distance is presented here. Segment-based GMPEs ranking shows different ranks, DSI and weights for each GMPE as compared to ranking considering entire distance. Finally, this study provides a list of GMPEs that perform best for the estimation of ground motion parameters in different parts of PI. This study shows that the GMPEs of HAHO-97, ATK-08, CAM-06, TOR-02, NDMA-10, and PEZA-11 perform better for the estimation of ground motion in most part of PI in the distance segment 0–200 km. The GMPEs of TOR-02, RAIY-07, and RAIY-07 (PI) perform best in the 200-maximum damage distance segment.

Correlation of densities with shear wave velocities and SPT N values

Site effects primarily depend on the shear modulus of subsurface layers, and this is generally estimated from the measured shear wave velocity (Vs) and assumed density. Very rarely, densities are measured for amplification estimation because drilling and sampling processes are time consuming and expensive. In this study, an attempt has been made to derive the correlation between the density (dry and wet density) and V-s/SPT (standard penetration test) N values using measured data. A total of 354 measured Vs and density data sets and 364 SPT N value and density data sets from 23 boreholes have been used in the study. Separate relations have been developed for all soil types as well as fine-grained and coarse-grained soil types. The correlations developed for bulk density were compared with the available data and it was found that the proposed relation matched well with the existing data. A graphical comparison and validation based on the consistency ratio and cumulative frequency curves was performed and the newly developed relations were found to demonstrate good prediction performance. An attempt has also been made to propose a relation between the bulk density and shear wave velocity applicable for a wide range of soil and rock by considering data from this study as well as that of previous studies. These correlations will be useful for predicting the density (bulk and dry) of sites having measured the shear wave velocity and SPT N values.

Seismic and well log driven structural and petrophysical analysis of the Lower Goru Formation in the Lower Indus Basin, Pakistan

The Sinjhoro concession is prolific gas-producing block situated on the eastern limb of the Lower Indus Basin in Pakistan. It contains several development and production (D & P) leases, which are producing gas from Cretaceous rocks. The present study aimed to evaluate the structural and petrophysical properties of the Lower Goru Formation using a 2D seismic and well-driven integrated study. A seismic driven time structure map of the Lower Goru Formation was generated, which depicted horst and graben structures oriented predominantly in a NNW-SSE direction. These normal faults are deep seated and potentially provide a vertical primary migration pathway to hydrocarbon flow. A prospective lead of 20 ms was identified in the northwestern portion of the structural map, which could be explored further. Besides this, a RMS amplitude map was generated within the target reservoir level to show the general sand body distribution within the reservoir. Our study revealed that the reservoir quality sands are deposited in the eastern portion of the study area. The identified lead is also located on a fair to good level of sand body which is producing from the well drilled to the south of the prospective area. Additionally, it is strongly recommended to conduct an infill seismic survey over and around the newly identified prospect in order to validate its existence and aerial outspreads. Well correlation, petrophysical data logs (PDLs) and cross-plot techniques were adopted to predict the petrophysical properties of the reservoir level. During the petrophysical study, two prospective zone were identified, with Zone-II showing more promising results for hydrocarbon presence than Zone-I. The present research has shown that integration of seismic attributes with petrophysical calculations can help to identify new prospective leads even in cases where there is less seismic data coverage.

Efficient Acquisition and Holistic Analysis of Rayleigh Waves

Surface-wave analysis is nowadays widely considered for a number of goals ranging from geotechnical investigations to seismic-hazard studies. The most common approach is surely represented by the analysis of active or passive multi-channel data used to depict the phase velocity spectrum from which dispersion curves are then depicted and inverted. The presented methodology attempts to obtain a robust sub-surface model in spite of the light equipment (a single [at least] bi-axial geophone) and the straightforward field procedures. The active method here presented can be considered as an improvement of the classical MFA (Multiple Filter Analysis) method and is based on the joint analysis of the vertical and radial group-velocity spectra, together with the Radial-to-Vertical Spectral Ratio (RVSR). After introducing the fundamental points charactering its implementation, a case study is presented also comparing the obtained sub-surface model with the one obtained considering a standard approach based on multi-channel active (MASW - Multichannel Analysis of Surface Waves) and passive (ESAC - Extended Spatial AutoCorrelation) data jointly considered with the Horizontal-to-Vertical Spectral Ratio (HVSR).

Combined Inversion of Electrical Resistivity and Transient Electromagnetic Soundings for Mapping Groundwater Contamination Plumes in Al Quwy'yia Area, Saudi Arabia

Time-domain electromagnetic (TEM) soundings and vertical electrical soundings (VES) were conducted to assess the subsurface groundwater contamination in Al Quwy’yia area through tracing the conductivity changes caused by leachate contamination of groundwater. Most of the contamination sources are coming from the incomplete sanitary system and the illegal dumping of wastewater along the lowland area outside the town. Contamination of the groundwater poses a major threat because most of the local inhabitants rely on ground water to supply up to 60% of their water needs for various life activities. TEM and VES data sets have been acquired along four longitudinal profiles to cover the most urban area of Al Quwy’yia. The combined inversion of VES and TEM data sets increase the resolving certainty of the subsurface resistivity models. The basement rock has the highest resistivity values, whereas the uncontaminated limestone has moderate resistivity response in comparison with the contaminated zones, which have a lower resistivity response. The constructed cross-sections and resistivity slice maps along the area provide valuable information about the shallow seepage from the septic tanks, as well as the deep infiltration from the dump site at the southern part of the study area.

Region-specific deterministic and probabilistic seismic hazard analysis of Kanpur city

A seismic hazard map of Kanpur city has been developed considering the region-specific seismotectonic parameters within a 500-km radius by deterministic and probabilistic approaches. The maximum probable earthquake magnitude (Mmax) for each seismic source has been estimated by considering the regional rupture characteristics method and has been compared with the maximum magnitude observed Mmaxobs

Pseudo-Spectral Damping Reduction Factors for the Himalayan Region Considering Recorded Ground-Motion Data

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Relationship between Intensity and Recorded Ground‐Motion and Spectral Parameters for the Himalayan Region

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Selection of representative shear modulus reduction and damping curves for rock, gravel and sand sites from the KiK-Net downhole array

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Soil Void Ratio Correlation with Shear Wave Velocities and SPT N Values for Indo-Gangetic Basin

and Kijko method. The best suitable ground motion prediction equations (GMPE) were selected from 27 applicable GMPEs based on the ‘efficacy test’. Furthermore, different weight factors were assigned to different Mmax values and the selected GMPE to calculate the final hazard value. Peak ground acceleration and spectral acceleration at 0.2 and 1 s were estimated and mapped for worst-case scenario and 2 and 10% probability of exceedance for 50 years. Peak ground acceleration (PGA) showed a variation from 0.04 to 0.36 g for DSHA, from 0.02 to 0.32 g and 0.092 to 0.1525 g for 2 and 10% probability in 50 years, respectively. A normalised site-specific design spectrum has been developed considering three vulnerable sources based on deaggregation at the city center and the results are compared with the recent 2011 Sikkim and 2015 Nepal earthquakes, and the Indian seismic code IS 1893.