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Earthquake Effects on Buildings
Published in Bungale S. Taranath, Tall Building Design, 2016
The earthquake ground-shaking hazard for a given region or site can be determined in two ways: deterministically or probabilistically. A deterministic hazard assessment estimates the level of shaking, including the uncertainty in the assessment, at the building site for a selected earthquake scenario. Typically, the earthquake is selected as the maximum-magnitude earthquake considered to be capable of occurring on an identified active earthquake fault; this maximum-magnitude earthquake is termed a characteristic earthquake. A deterministic analysis is often made when there is a well-defined active fault for which there is a sufficiently high probability of a characteristic earthquake occurring during the life of the building. The known past occurrence of such an earthquake, or geologic evidence of the periodic occurrence of such earthquakes in the past, is often considered to be indicative of a high probability for a future repeat occurrence of the event.
Probabilistic seismic hazard assessment
Published in Sreevalsa Kolathayar, T.G. Sitharam, Earthquake Hazard Assessment, 2018
Sreevalsa Kolathayar, T.G. Sitharam
Probabilistic seismic hazard analysis (PSHA) is a well-established methodology, and was initially developed by Cornell (1968). It is a well-known fact that many uncertainties are involved in earthquake location and size, which makes the problem complex. PSHA provides a framework in which these uncertainties can be identified, quantified, and combined in a rational manner to give a complete picture of the seismic hazard (Kramer, 1996). Deterministic seismic hazard analysis (DSHA) considers just one (or sometimes a few) maximum magnitude–distance scenario, whereas PSHA considers contributions from all the earthquakes occurring at a source. PSHA also considers the effect of earthquake occurrence at any location in the fault. Thus, it considers the uncertainties in (1) the location of earthquake occurrence, (2) the magnitude of the earthquake, (3) the source-to-site distances, and (4) attenuation relations. The most recent knowledge of seismic activity in the region has to be used to evaluate the hazard, incorporating uncertainty associated with different modeling parameters, as well as spatial and temporal uncertainties. Peak ground acceleration (PGA) estimated from PSHA handles immeasurable uncertainties and is restricted to the design of noncritical construction and planning. This chapter describes in detail the methodology adopted for PSHA to evaluate PGA and spectral acceleration (Sa) values at the rock level for the study area. The hazard analysis will be described in detail with emphasis on the unique approach followed in the present study where different methodologies were adopted in modeling the sources and other parameters.
Loading magnitude for rock tunnel during earthquake estimated by dynamic measurement at an actual tunnel
Published in Daniele Peila, Giulia Viggiani, Tarcisio Celestino, Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2020
In this study, a series of static numerical analysis using a frame model is conducted to estimate rough loading magnitude to simulate strain of lining which was measured in an actual tunnel during a large earth quake. Major conclusions include: In order to simulate the strain mode of the tunnel lining measured during the earthquake, a static load of vertical and horizontal pressure with k-ratio 0.5 can be applied.According to the simulation, Pv = 26 kPa is the most possible maximum magnitude of loading during the earthquake.
Site Specific Hazard Assessment and Multi-Level Seismic Performance Evaluation of Historical Mosque
Published in International Journal of Architectural Heritage, 2023
Özden Saygılı, José V. Lemos, Saed Moghimi
Seismic hazard assessment helps to evaluate the potential damage and consequences that might occur in a specific area as a result of an earthquake. The most common method used in seismic hazard assessment is the probabilistic seismic hazard analysis (PSHA), which integrates information about seismicity, fault geometry, and ground motion. The results of PSHA provide a probabilistic estimate of the maximum ground motion that may be experienced at a particular location over a given time period, and can be used to evaluate the seismic risk of a particular area. The seismic sources are determined based on geological, geophysical, and seismological studies. The information obtained from these studies helps in defining the seismic hazard created by these sources. The next step is to determine the parameters that describe the earthquake activity of each source. These parameters include earthquake frequency, magnitude, and ground motion prediction. The results of the probabilistic seismic hazard analysis are presented in the form of hazard maps, which show the probability of ground motion occurring in different parts of the region. The maximum magnitude associated with each seismic source is determined by considering the maximum of either the largest observed earthquake or the largest earthquake predicted by empirical relationships such as the Wells and Coppersmith (1994) model. Determination of seismic sources were based on the observed surface ruptures caused by earthquakes, the change of the fault azimuth according to the main stress pattern of the region and the variation of the slip rate value on the fault traces (Figure 7).
Comprehensive Seismicity, Seismic Sources and Seismic Hazard Assessment of Assam, North East India
Published in Journal of Earthquake Engineering, 2020
Knowledge of maximum possible earthquake magnitude Mmax is required in the engineering application such as in estimation of seismic hazard analysis, maximum magnitude is an important input key parameter used in the seismic design. Indeed, Mmax is the upper limit or largest possible earthquake that can be produced by a seismic source in the area. There is no well-established relation or methodology to find the maximum magnitude [Kijko and Singh, 2011]. However, to estimate the maximum magnitude of seismic sources there are various popular methods viz. Wells and Coppersmith [1994], Gupta [2002], Mueller [2010], Kijko and Sellevoll [1989], Kijko [2004], Hall [1982], Stein and And Hanks [1998], and Jin and Aki [1988]. In this study, Gutenberg–Richter (G–R) truncated law [1944], Kijko [2004], and Gupta [2002] methods have been used to calculate the maximum magnitude, and these values are used as the maximum magnitude in further study. The maximum magnitude obtained using these methods are shown in Table 5. From Tables 4 and 5, it is observed that highlighted faults have more a- and b-values than other faults and maximum probable magnitude is also high. Hence, only these 17 source zones have taken for seismic hazard analysis and it is also observed that Lohiti, Oldham, and Sagging faults provide maximum probable magnitude of 9.5, 8.6, and 8.8. However, these faults have experienced magnitude 8.6, 8.1, and 8.2 in the past, respectively. In addition to this, Lohiti thrust is located at the juxtaposition of three mountain ranges such as Himalayan belt, Mishmi hill range, (NW of Shan-Malayasia Plate) and Naga–Patkai–Arakan range. However, it has been established that these tectonic zones are geodynamically active and may cause a higher magnitude of >8. However, in the recent past Lohiti has experienced an event of magnitude Mw >8.5, and recently in 2000 and 2013 Mw 6.8 and Mw 5.3 occurred around this fault. Sagging fault experienced Mw 8.2 in 1908 and still showing the more seismic activity. However, a total of 16 events were found with magnitude of Mw > 6 and 4 events with magnitude >Mw 7––a indication of higher magnitude earthquake in future. Oldham is located in Shillong plateau region where main cause of earthquake is inter-continental collision and intra-plate seismic activity, and in the past it has been experienced an earthquake of magnitude 8.1 in 1950. However, there is a possibility of higher magnitude in and around this region in future, the maximum observed magnitude and characteristic of the faults are shown in Table 6. However, the choice of maximum magnitude for some of faults such as Samin and Lohiti thrusts are conservative as we have found higher maximum probable magnitude 8.1 and 9.5 that contradict the maximum magnitude and length of fault relation. Since these faults are already experienced 7.6 and 8.1 magnitude earthquake in the past decade, we could say that there is possibility of the occurrence of these kinds of earthquakes in these fault regions.