Cal. Government Code § 831.25

(a) Neither a public entity nor a public employee is liable for any damage or injury to property, or for emotional distress unless the plaintiff has suffered substantial physical injury, off the public entity’s property caused by land failure of any unimproved public property if the land failure was caused by a natural condition of the unimproved public property. (b) For the purposes of this section, a natural condition exists and property shall be deemed unimproved notwithstanding the intervention of minor improvements made for the preservation or prudent management of the property in its unimproved state that did not contribute to the land failure. (c) As used in this section, “land failure” means any movement of land, including a landslide, mudslide, creep, subsidence, and any other gradual or rapid movement of land. (d) This section shall not benefit any public entity or public employee who had actual notice of probable damage that is likely to occur outside the public property because of land failure and who fails to give a reasonable warning of the danger to the affected property owners. Neither a public entity nor a public employee is liable for any damage or injury arising from the giving of a warning under this section. (e) Nothing in this section shall limit the immunity provided by Section 831.2. (f) Nothing in this section creates a duty of care or basis of liability for damage or injury to property or of liability for emotional distress.