In almost all cases, earthquake insurance is provided by means of an endorsement to a standard homeowners or business insurance policy. However, it can be provided as a stand-alone contract. The basis for most earthquake endorsement forms is language developed by the Insurance Services Office. Most insurers either use the ISO forms or modifications of the forms. One element common to all coverage forms surveyed is the provision that one or more earthquake shocks that occur within a seventy-two hour period are considered to be a single earthquake.
Aftershocks are common with earthquakes.
This provision makes an earthquake and its aftershocks one occurrence. This prevents compounding of coverage limits and the compounding of deductible amounts. Another common element is that coverage is excluded for flood or tidal wave of any nature, whether caused by, resulting from, contributed to, or aggravated by earthquake. Though most insurers will provide earthquake insurance, few of them actively market the coverage. It is usually provided only at the request of the insured.