The magnitude listed here is the "summary magnitude". For most events prior to 1898 this is the adjusted intensity magnitude, and for events after 1898 it is the surface wave magnitude. The list includes known earthquakes with a magnitude of at least 6 and selected smaller events. The smaller events since 1898 all have at least one reported magnitude of at least 5.8, even if the summary magnitude is smaller. Some of these magnitudes may be different than what is reported in the Southern California or Northern California Earthquake Catalog. In the future, we will adjust some of these magnitudes to reflect the best measure of the earthquake and label the type of magnitude being reported.

The date and time for each earthquake are given as "24 hour" time referenced to Greenwich Mean Time (now UTC). To convert a time to Pacific Standard Time (PST), subtract 8 hours. To convert a time to Pacific Daylight Time (PDT), where appropriate, subtract 7 hours.