summary and conclusions

The earthquake of June 21, 1920 originated a short distance west of Inglewood. The maximum intensity in the epicentral area was between VIII and IX in the Rossi-Forel scale. The disturbance was due to a small displacement of the rocks on the Inglewood-Newport-San Onofre fault or fault zone which parallels the Baldwin Hills-Los Cerritos ridge on the southwest and extends in a southeasterly direction apparently as far as the San Luis Rey River. The character of the motion in the epicentral area suggests that the displacement was probably vertical.

The area within which the shock was felt (eleven thousand square miles or twenty-nine thousand square kilometers) was small considering the high intensity of the shock. This probably means that the origin was close to the surface. The rapid decrease in intensity on going away from the epicenter is chiefly due to the unconsolidated character of the rock strata in this area. While the vibrations die out rapidly in passing through such materials the destructive effects are always greater than in areas similarly located with respect to the origin but which are underlain with more rigid rock.

The physiography, geology, and the recent seismic history of the Los Angeles coastal plain, remind us that earthquakes are to be expected in that area from time to time. But if the inhabitants will heed nature's warnings and take proper precautions in the location and construction of buildings and other structures, such earthquakes are not likely to do much damage.

First Page Preview

First page PDF preview
You do not currently have access to this article.