M. L. Sharma

Ground-motion prediction equations based on data from the himalayan and zagros regions

This study derives ground-motion prediction equations for the horizontal elastic response spectral acceleration for 5% damping for application to the Indian Himalayas. The present equations include a consideration of site category (rock/soil) and style-of-faulting (strike-slip/reverse). Due to a lack of near-field data from India, additional strong-motion data have been included from the Zagros region of Iran, which has comparable seismotectonics to the Himalayas (continental compression). A set of 201 records from 16 earthquakes were used within the regression. The derived model predicts similar ground motions to previously published equations for the Himalayan region but with lower standard deviations.

Run-up and Inundation Pattern Developed During the Indian Ocean Tsunami of December 26, 2004 Along the Coast of Tamilnadu (India)

The tsunami run-up, inundation and damage pattern observed along the coast of Tamilnadu (India) during the deadliest Indian Ocean tsunami of December 26, 2004 is documented in this paper. The tsunami caused severe damage and claimed many victims in the coastal areas of eleven countries, bordering the Indian Ocean. Along the coast of Indian mainland, the damage was caused by the tsunami only. Largest tsunami run-up and inundation was observed along the coast of Nagapattinam district and was about 10–12 m and 3.0 km, respectively. The measured inundation data were strongly scattered in direct relationship to the morphology of the seashore and the tsunami run-up. Lowest tsunami run-up and inundation was measured along the coast of Thanjavur, Puddukkotai and Ramnathpuram districts of Tamilnadu in the Palk Strait. The presence of shadow of Sri Lanka, the interferences of direct/receded waves with the reflected waves from Sri Lanka and Maldive Islands and variation in the width of continental shelf were the main cause of large variation in tsunami run-up along the coast of Tamilnadu.

A STRONG MOTION MODEL OF THE 2004 GREAT SUMATRA EARTHQUAKE: SIMULATION USING A MODIFIED SEMI EMPIRICAL METHOD

This paper presents a simplified technique to simulate strong ground motion from a finite source of an earthquake. The simplified technique is based on modifications made in the semi empirical technique given by Midorikawa [1993] and later modified by Joshi and Midorikawa [2004]. Modifications in this technique have been made to consider the effect of radiation pattern and seismic moment of the target earthquake. The coastal region of Sumatra Island was struck by a great earthquake of magnitude 9.0 (Mw) on 26th December, 2004. This earthquake is known for its release of high amount of energy and the devastating Tsunami. This earthquake was recorded at several broadband stations including a nearest broadband station located in Indonesia. The source of this earthquake is modeled by a finite rectangular rupture plane. Various locations of nucleation point and different values of rupture velocity have been tested before finalizing the rupture responsible for this earthquake. Iterative modeling and comparison of simulated and observed record due to final model suggests that the rupture initiated at the western end of the rupture plane at a depth of 38 km and started propagating in all direction with a rupture velocity of 3.0 km/s. The final model has been used to simulate record at MDRS and VISK stations located at the coastal region of India and simulated records are compared with observed records at these stations. The comparisons confirm the suitability of final model for predicting strong ground motion and the efficacy of the approach in modeling great earthquake. Strong ground motion has been simulated for the Sumatra earthquake of 26th December, 2004 at various hypothetical stations surrounding the final model of rupture plane. The distribution of peak ground acceleration in the near source region has been computed from simulated record at these stations. The isoacceleration contours shows that high peak acceleration zones of the order of > 2 g are observed in the source zone of this earthquake which gradually decreases with distance. Using the parameters of final model of the Sumatra earthquake a great hypothetical earthquake at northern segment of Andaman ridge has been modeled and records have been simulated at Port Blair (POR) station located in the Andaman Island, India. The simulated records shows that peak ground acceleration of the order of 1.4 g can be observed at POR station due to a hypothetical earthquake in the Andaman Island suggesting high seismic hazard in this region.

Study of effect of seismic displacements on landslide susceptibility zonation (LSZ) in Garhwal Himalayan region of India using GIS and remote sensing techniques

Landslides are the most damaging and threatening aftereffect of seismic events in Garhwal Himalayas. It is evident from past seismic events in Uttarakhand, India that no other phenomena can produce landslides of so great in size and number as a single seismic event can produce. Landslide inventories are produced for the study area before and after the occurrence of Chamoli Earthquake using Panchromatic (PAN) sharpened Linear Imaging Self Scanning-III (LISS-III) images. A sudden increase in number of landslides after the earthquake is observed. Further, two Landslide Susceptibility Zonation (LSZ) maps have been derived using pre- and post-Chamoli Earthquake landslide inventories. The difference of two LSZ indicates that landslides are very complex phenomenon and are affected by static factors in seismic conditions also. An attempt has been made to estimate the seismic displacements using Differential Synthetic Aperture Radar Interferometry (DIn SAR). European Remote Sensing Satellite-1/2 (ERS-1/ 2) SAR images have been used for preparing differential interferogram. Geometric and temporal decorrelation in SAR images is very high in the study area, which limits the use of DInSAR for displacement estimation. Theoretical displacement has been estimated using fault displacement modeling parameters for Chamoli earthquake. Post-Chamoli earthquake landslide inventory is overlaid over displacement map for understanding the impact of seismic displacement pattern with other static factors on the occurrence of landslides. It is observed that distribution and size of landslides is affected by displacement pattern controlled by other static factors also.

Unbiased Estimation of Moment Magnitude from Body‐ and Surface‐Wave Magnitudes

Abstract For regression of variables having measurement errors, general orthogonal regression (GOR) is the most appropriate statistical procedure that yields a linear relation between the true values of the dependent ( y t ) and independent ( x t ) variables. However, the GOR procedure to obtain unbiased estimate of the dependent variable for a given error‐affected value of the predictor variable is not well addressed in the literature. In the conventional GOR approach, the error‐affected value of the predictor variable is substituted as such in the GOR relation, yielding biased estimates of y t . In another approach, the orthogonal projections of the given points on the GOR line are used to first estimate x t and then y t . In this study, a procedure making use of true points on the GOR line is proposed to obtain improved estimates of y t . The proposed GOR procedure is applied to the magnitude conversion problem between m b to M w and M s to M w , using real data set. The absolute average differences of the estimates obtained and their standard deviations are compared, indicating that the proposed GOR procedure provides improved estimates of the dependent variable ( y t ) compared with the conventional GOR approach. The improved unified magnitudes obtained using the proposed GOR procedure will result in more realistic seismic hazard for a given catalog and seismotectonic environment.

Usefulness of synthetic aperture radar (SAR) interferometry for digital elevation model (DEM) generation and estimation of land surface displacement in Jharia coal field area

Land surface displacement is a phenomenon of ground movement, which may occur due to various reasons including unplanned mining. The quantification of land surface displacement through conventional field surveys is based on sparingly distributed point data, which may be insufficient for many applications. A detailed spatial and temporal monitoring of land surface displacements through remote sensing-based synthetic aperture radar (SAR) interferometry may be valuable. Over the last two decades, differential SAR interferometry (DInSAR) has been effectively used globally for the estimation of spatial land surface displacements caused due to natural and man-made hazards. However, it has not gained momentum in India, where occurrences of natural and man-made hazards are a common phenomenon. In this article, preliminary results from DInSAR to measure land surface displacement in Jharia coal fields have been presented. DInSAR results effectively identified the land surface displacement due to several mining activities in the region during a one-month period.

Potential of SAR intensity tracking technique to estimate displacement rate in a landslide-prone area in Haridwar region, India

Landslides constitute one of the major natural hazards that could cause significant loss of life and various human settlements. Mansa Devi hill near Haridwar city has encountered with such potential hazard for several years due to the instability of the slopes. Therefore, preparedness both on regional and site-specific basis at spatial level in the form of surface movements is extremely important to diminish the damage of human life and settlements. Though the surface movement measurement through field-based technique is always very accurate, this technique is time-consuming and unfeasible over a widely affected region. Therefore, areal and satellite remote sensing is gaining importance in landslide investigation due to its wide coverage. In recent years, synthetic aperture radar has already proven its potential for mapping ground deformation due to earthquake, landslide, volcano, etc. Therefore, in this study, an attempt has been made to identify the potential landslide-affected region in Mansa Devi area using one multi-temporal SAR technique and intensity tracking technique. Intensity tracking technique has identified significant mass movement in the landslide-affected region where the other conventional multi-temporal technique, SBAS, fails. An error analysis has been carried out in order to demonstrate the applicability of intensity tracking technique. This study demonstrated that intensity tracking can be considered as an alternative to conventional interferometry for the estimation of land surface displacement when latter is limited by loss of coherence due to rapid and incoherent surface movement and/or large acquisition time intervals between the two SAR images.

Inclusion of earthquake strong ground motion in a geographic information system-based landslide susceptibility zonation in Garhwal Himalayas

Garhwal Himalayas are seismically very active and simultaneously suffering from landslide hazards. Landslides are one of the most frequent natural hazards in Himalayas causing damages worth more than one billion US

Surface displacement estimation using multi-temporal SAR Interferometry in a seismically active region of the Himalaya

and around 200 deaths every year. Thus, it is of paramount importance to identify the landslide causative factors to study them carefully and rank them as per their influence on the occurrence of landslides. The difference image of GIS-derived landslide susceptibility zonation maps prepared for pre- and post-Chamoli earthquake shows the effect of seismic shaking on the occurrence of landslides in the Garhwal Himalaya. An attempt has been made to incorporate seismic shaking parameters in terms of peak ground acceleration with other static landslide causative factors to produce landslide susceptibility zonation map in geographic information system environment. In this paper, probabilistic seismic hazard analysis has been carried out to calculate peak ground acceleration values at different time periods for estimating seismic shaking conditions in the study area. Further, these values are used as one of the causative factors of landslides in the study area and it is observed that it refines the preparation of landslide susceptibility zonation map in seismically active areas like Garhwal Himalayas.

Multi-parameter algorithm for Earthquake Early Warning

The Indian subcontinent is one of the most earthquake-prone regions of the world. The Himalayas are well known for high seismic activity, and the ongoing northwards drift of the Indian plate makes the Himalaya geodynamically active. During the last three decades, several major earthquakes occurred at the plate interiors and boundaries in this subcontinent causing massive losses. Therefore, one of the major challenges in seismology has been to estimate long recurrence period of large earthquakes where most of the classical Probabilistic Seismic Hazard Approaches fail due to short catalogues used in the prediction models. Therefore, during the past few decades, the Himalayan region has been studied extensively in terms of the present ongoing displacements. In this context the present study has been carried out to estimate the surface displacement in a seismically active region of the Himalaya, in between Ganga and Yamuna Tear, using multi-temporal Synthetic Aperture Radar (SAR) Interferometry. A displacement rate of 6.2–8.2 mm/yr in N14°E direction of the Indian plate towards the Tibetan plate has been obtained. It has been noted that the estimated convergence rate using Differential SAR Interferometry technique is relatively low in comparison with those obtained from previous classical studies. The reported low convergence rate may be due to the occurrence of silent/quite earthquakes, aseismic slip, differential movement of Delhi Hardwar ridge, etc. Therefore, in view of the contemporary seismicity and conspicuous displacements, a study of long-term observations of this surface movement has been recommended in future through a time-series SAR Interferometry analysis.