A magnitude 5.7 earthquake struck off the Northern California coast on Thursday, June 4, followed by a magnitude 5.1 quake west of Petrolia. The U.S. Tsunami Warning Center issued no tsunami warning or threat, and USGS impact estimates pointed to a low likelih
A magnitude 5.7 earthquake jolted the waters off Northern California early Thursday, June 4—near a highly seismic spot where three tectonic plates meet—then a smaller quake followed minutes later.
The strongest earthquake struck just before 4 a.m. Pacific time, moving through the sea about 120 miles from McKinleyville. Around two hours later, another quake of magnitude 5.1 hit roughly 40 miles west of Petrolia in Humboldt County. Minutes after that, a magnitude 4.5 aftershock struck in nearly the same location.
USGS reports placed the Petrolia-area earthquakes at very shallow depths beneath the seafloor. Even so, there was no tsunami threat: the U.S. Tsunami Warning Center said no tsunami warning, advisory, watch, or threat was issued. USGS impact estimates also indicated a low likelihood of significant damage.
The quakes landed near the Mendocino Triple Junction, a region off Northern California’s coast where three tectonic plates meet. That matters in a state that already has more than 500 active faults—faults that scientists acknowledge they can’t time. Earthquakes, the public is often reminded, are not predictable.
How the ground keeps getting stressed
The Earth’s surface is shaped by slow-moving pieces of the outer crust and upper mantle. These are called tectonic plates. As they shift and interact—bumping, colliding, and grinding at their edges—stress builds along faults. When friction can’t hold, energy is released suddenly, sending seismic waves that produce an earthquake.
The United Nations describes four types of earthquakes: tectonic earthquakes, volcanic earthquakes, collapse earthquakes, and explosion earthquakes.
Even when alerts feel more frequent, long-term averages don’t necessarily change
People often wonder whether earthquakes are happening more often, especially with real-time notifications and widespread coverage. The U.S. Geological Survey says the overall rate of earthquakes has remained relatively stable over time.
The explanation is partly technological: any year can look busier because improvements in detection allow scientists to spot more small quakes than in the past.
Long-term global records dating back to 1900 show the Earth averages about 16 major earthquakes each year—defined as magnitude 7.0 or greater. Those years typically include 15 events in the 7.0 range and one event with magnitude 8.0 or higher. In 2024, there were 10 earthquakes of magnitude 7.0 or greater, with the strongest being a 7.5 in Japan.
Risk can still grow even if earthquakes don’t become more frequent
The question isn’t only how often earthquakes happen. The Federal Emergency Management Agency said in a 2023 report that the risk of being affected by an earthquake is growing as human and economic exposure increases and as more assets are built in high earthquake hazard areas.
For Thursday’s sequence. the immediate bottom line was clear: no tsunami warning. advisory. watch. or threat was issued. and USGS impact estimates pointed to a low likelihood of significant damage—even as the Mendocino Triple Junction continues to underscore how active and unpredictable California’s geology remains.
California earthquake Mendocino Triple Junction USGS 5.7 earthquake 5.1 earthquake Humboldt County tsunami warning center tectonic plates earthquake risk