The San Gregorio Fault is an active earthquake fault located off the coast of Northern California

Northern California

Northern California is the northern portion of the U.S. state of California. The San Francisco Bay Area , and Sacramento as well as its metropolitan area are the main population centers...

. The southern end of the fault is in southern Monterey Bay

Monterey Bay

Monterey Bay is a bay of the Pacific Ocean, along the central coast of California. The bay is south of San Francisco and San Jose, between the cities of Santa Cruz and Monterey....

, and the northern end is about 20 km northwest of San Francisco

San Francisco, California

San Francisco , officially the City and County of San Francisco, is the financial, cultural, and transportation center of the San Francisco Bay Area, a region of 7.15 million people which includes San Jose and Oakland...

, near Bolinas Bay

Bolinas Bay

Bolinas Bay is a small bay, approximately 5 miles wide, on the Pacific coast of California in the United States. It is in Marin County, north of the Golden Gate, approximately 15 miles northwest of San Francisco...

, where the San Gregorio intersects the San Andreas Fault

San Andreas Fault

The San Andreas Fault is a continental strike-slip fault that runs a length of roughly through California in the United States. The fault's motion is right-lateral strike-slip...

. Most of the San Gregorio fault trace

Fault trace

A fault trace is the intersection of a geological fault with the ground surface, leaving a visible mark. The term also applies to a line plotted on a geological map to represent a fault.-Source:*...

 is located offshore beneath the waters of Monterey Bay, Half Moon Bay

Half Moon Bay (California)

Half Moon Bay is a bay of the Pacific Ocean on the coast of San Mateo County, California. The bay is approximately semi-circular, hence the name half moon, with sea access to the south...

, and the Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, though it cuts across land near Point Ano Nuevo

Año Nuevo State Reserve

Año Nuevo State Park is a state park of California, USA, encompassing Año Nuevo Island and Año Nuevo Point, which are known for their pinniped rookeries. Located in San Mateo County, the low, rocky, windswept point juts out into the Pacific Ocean about south of San Francisco and the Golden Gate...

 and Pillar Point. The San Gregorio Fault is part of a system of coastal faults which run roughly parallel to the San Andreas.

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