Using a similar strategy , S. D. Malone and S. Bor analyzed the known intensities for the 1872 shock , then compared intensity patterns for a number of instrumentally recorded earthquakes that also occurred in the Pacific Northwest . A factor that was taken into consideration was that for earthquakes that have either circular or slightly elliptical isoseismal maps , the epicenter is usually close to the center of the pattern , but that for shocks where instrumental information are also available , the epicenter is sometimes not where it would have been assumed to be , had only the intensity information ( and no instrumental information ) been available . An isoseismal map of the 1949 Olympia earthquake was presented as an example of a distorted or convoluted pattern that was attributed to local geological conditions that either attenuated or amplified the seismic waves , and it was emphasized that not taking into account these local features could lead to a misinterpretation of the felt intensities and to a misplaced epicenter
1949 Olympia earthquake
1949 Olympia earthquake
1872 North Cascades earthquake