Cal. Civ. Code § 55.1-1240

If the dwelling unit or premises is damaged or destroyed by fire or casualty to an extent that the tenant's enjoyment of the dwelling unit is substantially impaired or required repairs can only be accomplished if the tenant vacates the dwelling unit, either the tenant or the landlord may terminate the rental agreement. The tenant may terminate the rental agreement by vacating the premises and within 14 days thereafter, serving on the landlord a written notice of his intention to terminate the rental agreement, in which case the rental agreement terminates as of the date of vacating. If continued occupancy is lawful, § 55.1-1411 shall apply.
The landlord may terminate the rental agreement by giving the tenant 14 days' notice of his intention to terminate the rental agreement on the basis of the landlord's determination that such damage requires the removal of the tenant and that the use of the premises is substantially impaired, in which case the rental agreement terminates as of the expiration of the notice period.
If the rental agreement is terminated, the landlord shall return all security deposits in accordance with § 55.1-1226 and prepaid rent, plus accrued interest, recoverable by law unless the landlord reasonably believes that the tenant, an authorized occupant, or a guest or invitee of the tenant was the cause of the damage or casualty, in which case the landlord shall provide a written statement to the tenant for the security and prepaid rent, plus accrued interest based upon the damage or casualty, and may recover actual damages sustained pursuant to § 55.1-1251 . Proration for rent in the event of termination or apportionment shall be made as of the date of the casualty.