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City of Santa Ana Emergency Operations Plan <br />Part I Basic Plan <br />Yet the San Andreas is only one of numerous known active faults that crisscross Southern California. A fault is <br />considered active if it has ruptured within the last 11,000 years and potentially active if it has ruptured in the last <br />1.8 million years. Large faults that would affect the Orange County area include the San Andreas, Newport - <br />Inglewood, Los Alamitos, Whittier, Elsinore, Chino and San Jacinto Faults. Smaller Orange County -area faults <br />include the Norwalk Fault, the El Modena and Peralta Hills Faults, as well as the newly studied San Joaquin Hills <br />and Puente Hills Faults. Beyond these known faults, there are potentially a number of "blind" faults, faults that <br />have not yet been discovered or mapped, underlying the surface of Southern California. The Whittier Narrows <br />Earthquake in October 1987 and the Northridge Earthquake in January 1994 occurred on blind faults. <br />Figure 34 Orange County Earthquake Fault Zones <br />N [Orange County <br />Fault Zones <br />C� O LCSANG&LSS <br />E C <br />�+ <br />NLLEa,oN r 9 <br />!O� CNN LTA <br />� SOD a <br />NmE UNINC. <br />s.N,N.N. NN N oaro� NN ��iF'P <br />N 9 <br />G� <br />\ T <br />T - <br />"INE � <br />.oN o <br />9� <br />°4 <br />o\ y NNINC a° <br />0 r �o <br />pis �C <br />mac, °C) ���4 NON <br />G <br />zoN� Fq Al!� �� aNNo <br />.o:: <br />04 <br />Legend ° <br />KI—FUuNS <br />Qary emnearN•s ` <br />Notes on Figure 34: The fault touching the right margin of the map is the Elsinore Fault but is incorrectly labeled the <br />Whittier Fault. The Whittier Fault lies at the top center where it is correctly labeled. The San Joaquin Hills Fault does not <br />appear on this map but runs along the 405 Freeway south of the City border. <br />Although the most famous of the faults, the San Andreas, is capable of producing an earthquake with a magnitude <br />of 8.0 or more on the Richter scale, some of the "lesser" faults have the potential to inflict greater damage on the <br />urban core of Orange County. Seismologists believe that a 6.0 earthquake on the Newport -Inglewood would result <br />34 <br />