Engineering Geology and Seismology Lecture#17 CE-312 Engineering Geology and Seismology Instructor: Dr Amjad Naseer Department of Civil Engineering N-W.F.P University of Engineering and Technology, Peshawar

Outlines of the Presentation Seismic Risk Seismic Hazard Assessment Deterministic Seismic Hazard Assessment (DSHA) Probablistic Seismic Hazard Assessment (PSHA)

Seismic Risk SEISMIC RISK refers to the amount of damage to be expected with a certain probability in a fixed period time. It is the composition of RISK =HAZARD * EXPOSURE * VULNERABILITY The hazard is controlled by Nature. Vulnerability and Exposure are controlled by humans. 4

Seismic Risk Seismic hazard is the probability of observing a certain ground shaking (e.g., PGA, macro-seismic intensity, etc.) in a fixed time period. Vulnerability is the tendency of a structure to suffer damage. Exposed value is an economic, but also social, quantification of the object exposed to earthquakes. 5

Nature Engineers Planners

Seismic Hazard Zoning Map 7 N-W.F.P UET, Peshawar 7

“Natural” Disasters and Casualties

Economic Impact of Earthquakes The Gross National Product (GNP) is the total dollar value of all final goods and services produced for consumption in society during a particular time period.

Seismic Risk Mitigation HAZARD * EXPOSURE * VULNERABILITY * COST Assess Control Reduce Balance

Deterministic Seismic Hazard Assessment (DSHA) The different sources of seismicity around a site are identified and an earthquake scenario is fixed for each of source. The location of the scenario is usually taken to be at the least favourable location, in other words at the closest approach to the site, possibly such that the site will also experience forward directivity effects. The magnitude of each scenario is a more difficult subject to select. However, the results of a deterministic analysis are far more sensitive to the choice of upper-bound magnitude than a probabilistic analysis. The term generally used to define the size of the controlling event is the Maximum Credible Earthquake (MCE), although there are many who argue for this term to be abandoned. 11

Deterministic Seismic Hazard Assessment (DSHA) Once the design scenarios are fixed in terms of magnitude and distance from the site, it is a very straightforward operation to estimate the resulting levels of ground motion using attenuation relationships. The most onerous ground motion can then be taken as the basis for design, although in some cases it may be necessary to consider more than one scenario if the ground motions do not show a single clearly dominant case. 12

Deterministic Seismic Hazard Assessment (DSHA) 13

Deterministic Seismic Hazard Assessment (DSHA) Once the design scenarios are fixed in terms of magnitude and distance from the site, it is a very straightforward operation to estimate the resulting levels of ground motion using attenuation relationships. The most onerous ground motion can then be taken as the basis for design, although in some cases it may be necessary to consider more than one scenario if the ground motions do not show a single clearly dominant case. 14