Size of Earthquakes

Abstract

Earthquake size is one of the most fundamental source parameters used in seismic catalogs. A reliable measure of the "size" of an earthquake is essential for seismological, geological, engineering, and scientific research. The size of a seismic source is measured using two parameters; damage caused (intensity) and energy released (magnitude). Intensity describes the strength of a seismic event in terms of human recognition, affected region, damage to structures. Intensity scales are valuable not only for the pre-instrumental period for historical earthquakes but also for seismic risk analysis. The intensity scale is classified by macroseismic scales. Intensity depends on local geological conditions, distance from the source that make the objective estimates difficult. The concept of magnitude was introduced by Richter to provide an objective measure of earthquake size. The advent of seismic recording systems made it possible to determine the strength of a seismic event from instrumental data. The magnitude of an earthquake provides quick information on the strength of a seismic event for the public and are essential for cataloging. Changes in instrumentation and magnitude formulation resulted from the calculation of different magnitude scales. In order to obtain a non-saturating uniform magnitude scale, seismic moment magnitude (Mw) is developed based on source parameters.