Mezue ahịrịokwu na-esonụ: Site n'ụzọ nkà mmụta ala, ala ọma jijiji nke El Centro nke 1940 n'ihe ọ̀tụ̀tụ̀ ike nke Mercalli. Ọ bụ ya bụ nnukwu ala ọma jijiji mbụ e ji ígwè seismograph nke na-arụ ọrụ ike, nke dị n'akụkụ ebe e mebiri emebi, dekọọ. A na-amụ ya nke ọma site na ndị injinia na-arụ ọrụ ma chee na ọ bụ ihe a na-ahụkarị ruo mgbe e mepụtara ya.
Ala ọma jijiji mere na Northridge n'afọ 1994. N'ógbè a, usoro mmụta ala na-achịkwa site na mgbanwe nke tectonic plate boundary site na rift gaa na transverse fault. Akụkụ ndịda nke San Andreas Fault na-ejikọ akụkụ ndịda nke East Pacific Rise. N'ihi ya, ala ọma jijiji na-emekarị n'ógbè ahụ, a na-agbatịkwa elu ala, nke na-eme ka ala ahụ na-emikpu n'ala ka oge na-aga.