Deterministic Seismic Hazard Analysis (DSHA)

DETERMINISTIC SEISMIC HAZARD ANALYSIS (DSHA)

• This type of analysis is done for a particular earthquake, either assumed or realistic.

• The DSHA approach uses the known seismic sources sufficiently near the site and available historical seismic and geological data.

These data are used to generate discrete, single-valued events or models Is of ground d motion at the site.

Typically one or more earthquakes are specified by magnitude and location with respect to the site.

Usually the earthquakes are assumed to occur on the portion of the site closest to the site.

Four Steps in DSHA

Deterministic Seismic Hazard Analysis consists of four steps

1. Identification and characterization of all sources.

2. Selection of source – site distance parameter

3. Selection of the "controlling earthquake"

4. Definition of hazard using controlling earthquake.

1. dentification and characterization of all earthquake deupd sources capable of producing significant ground motion at the site.

2. Selection of a source-to-site to-site distance parameter for each source zone (R₁, R₂ and R₃). In most DSHA's the shortest distance between the source zone and the site of interest is selected.

3. Selection of the controlling earthquake generally supd expressed in terms of some ground motion parameter, at the site.

The selection is made by comparing the levels of shaking produced by earthquakes (identified in step 1) assumed to occur at the distances identified in step 2.

The controlling earthquake is described in terms of the boodi size (usually expressed as magnitude) and distance from the site.

4. The hazard at the site is formally defined, usually in terms of the ground motions produced at the site by the controlling earthquake.

Its characteristics are usually described by one or more ground motion parameters obtained from predictive relationships of the types.

The DSHA procedure is shown schematically in (fig. 5.7).

Advantages

1. Peak acceleration, peak velocity, and response spectrum noi ordinates are commonly used to characterize the seismic hazard.

2. The DSHA appears to be a very simple procedure.

3. DSHA provides a straightforward framework for bemuaan evaluation of worst-case ground motions.

Disadvantages

 (i) It provides n no information on the likelihood of occurrence of the controlling earthquake.

(ii) Perhaps most important, DSHA involves subjective decisions, particularly regarding earthquake potential.

Applications

This analysis is used for some significant structures such as:

• Nuclear power plants

• Large dam

• Large bridges

• Hazardous waste containment facilities

• As cap for probabilistic analysis