For example, some districts prefer to use peak acceleration, others use peak velocity, and more sophisticated uses require response spectral ordinates. Finally, the calculations require formulae that give the required hazard indicators for a given earthquake size and distance.

Zones of higher seismicity in the continental interior may be the site for intraplate earthquakes) and tend to be drawn as broad areas, based on historic records, like the 1812 New Madrid earthquake, since specific causative faults are generally not identified as earthquake sources.Įach zone is given properties associated with source potential: how many earthquakes per year, the maximum size of earthquakes ( maximum magnitude), etc. The well known San Andreas Fault is illustrated as a long narrow elliptical zone of greater potential motion, like many areas along continental margins associated with the Pacific ring of fire. Zones of similar potential earthquake shaking are thus determined and drawn on maps. The regional geology and seismology setting is first examined for sources and patterns of earthquake occurrence, both in depth and at the surface from seismometer records secondly, the impacts from these sources are assessed relative to local geologic rock and soil types, slope angle and groundwater conditions. Allin Cornell in 1968 and, depending on their level of importance and use, can be quite complex. Surface motion map for a hypothetical earthquake on the northern portion of the Hayward Fault Zone and its presumed northern extension, the Rodgers Creek Fault ZoneĬalculations for determining seismic hazard were first formulated by C.

Usgs seismic calculator