Magnitude of earthquakes

This definition of the magnitude of earthquake is used for the records of Wood Anderson type torsion seismograph. This has a dampening equal to 80% of the critical natural, period of 0.8 second and a magnification of 2800. 

The relation between frequency and magnitude of earthquakes in a large seismically active region is given by the empirical Gutenberg-Richter law [20]... 

Figure 6.9 summarizes the result of Equation (6.87) for site class A. The six curves (from top to bottom) show the log o PGA versus the magnitude of earthquake M for six levels of distance, namely 10, 50, 100, 250, 500 and 1000 km. This chart can be used for prediction of peak ground acceleration in the design process. One first estimates the closest fault from the site so the corresponding curve can be selected. This curve shows the estimated peak ground acceleration under different levels of earthquake, which may be estimated by neural networks [194]. 

Table 15-3. Correlation between fault length and maximum magnitude of earthquake...

Richter scale (Charles Francis Richter) Richter develops a scale to describe the magnitude of earthquakes it is still used today. 

Coefficient of active earth pressure at rest Horizontal seismic coefficient Vertical seismic coefficient Yield coefficient Earthquake magnitude Constrained Modulus Local magnitude Surface wave magnitude Moment magnitude of earthquake Porosity Initial porosity... 

In ECS the earthquake motion at a site is represented by an elastic response spectmm in terms of spectral acceleration values (Annex A of ECS Part 1 additionally represents seismic action in the form of an elastic displacement response spectrum). The shape of the elastic response spectrum for each country may be found in its National Aimex, and it is the same for the two levels of seismic performance, i.e., for the no-collapse requirement as well as for the damage limitation requirement. It is also noted that in selecting the appropriate shape of the spectrum, consideration should be given to the magnitude of earthquakes that contribute most to the seismic hazard as defined in PSHA, rather than on conservative upper limits (e.g., the maximum credible earthquake). Regarding magnitude, two types of spectra are recommended,... 

The values of T, Tc, Tp, and S for the five standard ground types A to E are meant to be defined by each country in the National Annex to Eurocode 8, depending on the magnitude of earthquakes contributing the most to the hazard. The geological conditions at the site may also be taken into account, in addition to the properties of the top 30 m of ground, to determine these values. 

Magnitude-frequency relationship. Define the likely magnitudes of earthquakes that may be produced by each source and the associated frequencies of occurrence. 

Wyss M (1979) Estimating maximum expectable magnitude of earthquakes from fault dimensions. Geology 7 336-340... 

To provide a comparative example. Table 1 lists the order of magnitude of earthquake stresses... 

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