PART 1 DEALS WITH THE DYNAMIC ASPECTS OF THE SUBJECT: MATHEMATICAL ANALYSIS OF SYSTEMS SUBJECTED TO INDEPENDENT VIBRATIONS BY MEANS OF MATHEMATICAL MODELS. THE ANALYTICAL SYSTEMS USED ARE NON-LINEAR SYSTEMS, HYDRODYNAMICS AND NUMERICAL METHODS. PART 2 EXAMINES SEISMIC MOVEMENTS, THE DYNAMIC BEHAVIOUR OF STRUCTURES AND THE BASIC CONCEPTS OF THE SEISMIC DESIGN OF STRUCTURES.

Fundamentals of earthquake engineering

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Selection of earthquake ground motion records: A state-of-the-art review from a structural engineering perspective

The important role played by the duration of ground shaking in the response of saturated soil deposits is universally acknowledged, but no such consensus exists regarding the degree of influence that duration exerts on structural damage. There are several hundred papers in the literature that link structural damage to parameters related either directly or indirectly to the duration of strong ground motion. The conclusions of these studies differ widely with regard to the influence of strong-motion duration on structural demand. This paper provides a summary and critical review of the literature on this subject. It is found that studies employing damage measures related to cumulative energy usually find a positive correlation between strong-motion duration and structural damage, while studies employing damage measures using maximum response generally do not find strong correlations between duration and damage.

A State-of-Knowledge Review of the Influence of Strong-Motion Duration on Structural Damage

The 2015 Gorkha Nepal earthquake caused tremendous damage and loss. To gain valuable lessons from this tragic event, an earthquake damage investigation team was dispatched to Nepal from 1 May 2015 to 7 May 2015. A unique aspect of the earthquake damage investigation is that first-hand earthquake damage data were obtained 6 to 11 days after the mainshock. To gain deeper understanding of the observed earthquake damage in Nepal, the paper reviews the seismotectonic setting and regional seismicity in Nepal and analyzes available aftershock data and ground motion data. The earthquake damage observations indicate that the majority of the damaged buildings were stone/brick masonry structures with no seismic detailing, whereas the most of RC buildings were undamaged. This indicates that adequate structural design is the key to reduce the earthquake risk in Nepal. To share the gathered damage data widely, the collected damage data (geo-tagged photos and observation comments) are organized using Google Earth and the kmz file is made publicly available.

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The 2015 Gorkha Nepal Earthquake: Insights from Earthquake Damage Survey

The effect of weak interlayer on the failure pattern of rock mass around tunnel – Scaled model tests and numerical analysis

Seismic hazard maps have been prepared for Northeast India based on the uniform hazard response spectra for absolute acceleration at stiff sites. An approach that is free from regionalizing the seismotectonic sources has been proposed for performing the hazard analysis. Also, a new attenuation model for pseudo-spectral velocity scaling has been developed by using 261 recorded accelerograms in Northeast India. In the present study, the entire area of Northeast India has been divided into 0.1° grid size, and the hazard level has been assessed for each node of this grid by considering the seismicity within a 300-km radius around the node. Using the past earthquake data, the seismicity for the area around each node has been evaluated by defining a and b values of the Gutenberg-Richter recurrence relationship, while accounting for the incompleteness of the earthquake catalogue. To consider the spatial distribution of seismicity around each node, a spatially smoothed probability distribution function of the observed epicentral distances has been used. Uniform hazard contours for pseudo-spectral acceleration as the hazard parameter have been obtained for an exposure time of 100 years and for 50% confidence level at different natural periods for both horizontal and vertical components of ground motion. The trends reflected by these contours are broadly consistent with the major seismotectonic features in the region. DOI: 10.1193/1.2163914

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A Probabilistic Seismic Hazard Analysis of Northeast India

Delineation of probable seismic sources in India and neighbourhood by a comprehensive analysis of seismotectonic characteristics of the region

In its present form the response spectrum superposition technique provides only the highest peak of the response at various levels of a multistory structure. For better understanding of the progressing damage as the structure is subjected to successive excursions beyond the design level, and to estimate the number of times certain responses may be exceeded, it is essential to know all the peaks of the response, not just the highest peak. In this paper, a probabilistic theory is presented, using order statistics, to find the expected, the most probable, or with any desired confidence level, the amplitudes of all the local maxima in the random response functions at any point in a multistory structure.

Order statistics of peaks in earthquake response

The seismic hazard analysis is concerned with getting an estimate of the strong-motion parameters at a site for the purpose of earthquake resistant design or seismic safety assessment. For generalized applications, seismic hazard analysis can also be used to prepare macro or micro zoning maps of an area by estimating the strong-motion parameters for a closely spaced grid of sites. Two basic methodologies used for the purpose are the “deterministic” and the “probabilistic” seismic hazard analysis (PSHA) approaches. In the deterministic approach, the strong-motion parameters are estimated for the maximum credible earthquake, assumed to occur at the closest possible distance from the site of interest, without considering the likelihood of its occurrence during a specified exposure period. On the other hand, the probabilistic approach integrates the effects of all the earthquakes expected to occur at different locations during a specified life period, with the associated uncertainties and randomness taken into account. The present paper gives a critical and detailed description of both deterministic and probabilistic approaches for seismic hazard analyses. A large number of example results are presented to illustrate the implementations of the two approaches. The results of the probabilistic approach are able to account for the effects of all the controlling factors in a balanced way, and can thus be considered more reliable. The advantages quoted in favour of using the deterministic approach can simply be achieved via deaggregation of the probabilistic hazard analysis.

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I.D. Gupta

Papers

A Probabilistic Seismic Hazard Analysis of Northeast India

Delineation of probable seismic sources in India and neighbourhood by a comprehensive analysis of seismotectonic characteristics of the region

Order statistics of peaks in earthquake response

The state of the art in seismic hazard analysis

Response spectral attenuation relations for in-slab earthquakes in Indo-Burmese subduction zone