California Code, Health and Safety Code - HSC § 19163

(a) Any seismic retrofit of any building identified pursuant to paragraph (1) of subdivision (a) of Section 19161 as being hazardous to life in the event of an earthquake shall provide for the reasonable adequacy of all of the following:

(b) Any seismic retrofit of any building identified pursuant to paragraph (2) of subdivision (a) of Section 19161 as potentially hazardous shall comply with a nationally recognized model code relating to the retrofit of existing buildings or substantially equivalent standards. If the city, county, or city and county adopts local amendments to those provisions, it shall determine that the amendments are consistent with Section 17958.5.

(c)Seismic retrofit of any building or portions of any building shall be designed to resist and withstand the seismic forces from any direction as set forth in the building seismic retrofit standards using the allowable working stresses adopted pursuant to this article.

(d) The governing board of any city, city and county, or county may establish, by ordinance, standards and procedures to fulfill the intent of paragraph (2) of subdivision (a) without regard to the remainder of the requirements specified above.