An Introductory Geology Exercise on Contouring Intensities for the 1989 Loma Prieta Earthquake

Abstract

Following the October 17, 1989, Loma Prieta earthquake, students in several introductory geology classes were asked to complete a questionnaire that included questions concerning where they were at the time of the quake and the ground shaking effects at that site. As part of the Geology of California class, students used the Modified Mercalli Scale to assign an intensity value on the basis of the questionnaire responses and then plotted the values obtained on regional maps. A compilation of data from 133 responses revealed that ground shaking was most intense near the epicenter, but that higher intensities were experienced in northwest-trending belts of presumably weaker bedrock. The assigned values are probably somewhat higher than those that would be assigned by professional geologists and seismologists. The exercise was a very effective method of teaching students about ground shaking, as indicated by the number of correct responses to a subsequent exam question.