Mezue ahịrịokwu na-esonụ: Ihe omume 1971 bụ nke mbụ n'usoro (1987 Whittier Narrows, 1991 Sierra Madre,
1994 Northridge) nke ala ọma jijiji na-emebi ihe nke mere na mgbagwoju anya na mpaghara Los Angeles. Ihe omume ndị a kpalitere mkparịta ụka gbasara oke ala ọma jijiji nke nwere ike ime site na otu n'ime mmebi, ọkachasị na Transverse Ranges, mana isi ihe nyocha nke ala ọma jijiji na California na-abụkarị San Andreas Fault na mmebi ndị ọzọ metụtara ya. Ọ bụ ezie na enweghi data paleoseismic banyere ọdịiche dị na mpaghara Los Angeles, igwu olulu n'otu ebe na Sierra Madre-Cucamonga Fault kpughere na nnukwu ala ọma jijiji abụọ mere n'akụkọ ihe mere eme na afọ 15,000 gara aga.