San Mateo County

Earthquakes Near Half Moon Bay, California

Real-time earthquake monitoring for Half Moon Bay and surrounding areas within 25 miles. Located in the SF Peninsula / Millbrae / Pacifica region along the San Andreas Fault.

Within 25mi

7,087

total earthquakes

30-Day Activity

recent earthquakes

Avg Magnitude

1.20

Max Recorded

3.9

Recent Activity Near Half Moon Bay

40 earthquakes recorded within 25 miles of Half Moon Bay in the last 30 days. The largest was M2.5.

Earthquake Risk in Half Moon Bay

Half Moon Bay is located in San Mateo County, California, one of the most seismically active regions in the United States. The city sits within the San Francisco Bay Area, which is traversed by several major fault systems.

The nearest major fault to Half Moon Bay is the San Andreas Fault. This fault system is capable of producing earthquakes that could cause significant ground shaking in the area. Residents are encouraged to be prepared with emergency supplies and an earthquake plan.

Half Moon Bay Earthquake FAQ

Is Half Moon Bay at risk for earthquakes?

Yes, Half Moon Bay is located in San Mateo County within the seismically active San Francisco Bay Area. The region sits near several major fault systems, including the San Andreas Fault. Scientists estimate a 72% probability of a magnitude 6.7 or greater earthquake in the Bay Area within the next 30 years.

What should I do if I feel an earthquake in Half Moon Bay?

If you feel shaking in Half Moon Bay, remember "Drop, Cover, and Hold On." Drop to your hands and knees, take cover under a sturdy desk or table, and hold on until the shaking stops. Stay away from windows, exterior walls, and anything that could fall. If you're outdoors, move away from buildings, power lines, and trees.

How do I report feeling an earthquake in Half Moon Bay?

You can report feeling an earthquake in Half Moon Bay using Bay Tremor's "Did You Feel It?" feature or through the USGS website. Your reports help scientists understand earthquake intensity distribution and improve hazard assessments for San Mateo County.

What is the nearest fault line to Half Moon Bay?

The nearest major fault to Half Moon Bay is the San Andreas Fault. This fault is part of the San Andreas Fault system and is capable of producing significant earthquakes. Residents should maintain emergency supplies and have an earthquake preparedness plan.

How often do earthquakes occur near Half Moon Bay?

The Bay Area, including areas near Half Moon Bay, experiences hundreds of small earthquakes each year. Most are too small to feel (below magnitude 2.0), but noticeable earthquakes occur regularly. Larger earthquakes (magnitude 4.0+) that are widely felt happen several times per year across the Bay Area.

What earthquake supplies should Half Moon Bay residents have?

Half Moon Bay residents should prepare an earthquake kit containing: 3-7 days of water (1 gallon per person per day), non-perishable food, flashlight, batteries, first aid kit, medications, important documents, cash, and a battery-powered radio. Also secure heavy furniture to walls and know how to shut off gas and electricity.

How would a San Andreas earthquake affect Half Moon Bay?

A major San Andreas Fault earthquake would cause significant shaking in Half Moon Bay. While the fault runs mostly through the Peninsula and South Bay, a magnitude 7.0+ event would be felt strongly throughout San Mateo County. The 1906 San Francisco earthquake (M7.9) caused widespread damage across the entire Bay Area.