How the Lake Almanor Earthquakes are Related to Lassen Volcanic National Park

Two magnitude 5 earthquakes hit the Lake Almanor area over a 12-hour span on Thursday afternoon and Friday morning. With this area so close to Lassen Volcanic National Park, which is famous for its volcanic and geological activity, it begs the question – are the earthquakes related to the volcanic activity of the park?

Lake Almanor is located near a junction of three significant geological land masses: the Sierra Nevada, Modoc Plateau, and the Cascade geo-provinces, which all have a connection to the formation of the Lassen Peak volcano. This intersection creates fault zones beneath Lassen Peak, the southernmost active volcano in the Cascade Range, leading to a high degree of fracturing in the region.

Lassen Volcanic National Park, known for its hydrothermal sites, displays substantial thermal activity under the volcano. The area’s relatively thin crust can fracture easily, causing both minor and major earthquakes which can create pathways for magma to reach the surface.

While major earthquakes don’t typically trigger lava flows in this area, they have been known to cause significant shaking. Lake Almanor’s tectonic structure is dominated by two primary fault zones: the northwest trending Tahoe-Mohawk Valley-Lassen and the north-south trending Hat Creek-Lake Almanor fault zones. These zones intersect at Lake Almanor, creating a basin that forms the basis for the lake.

A 5.7 magnitude earthquake in 2013 on the Mohawk fault zone led to substantial damage. This fault zone is known to potentially generate earthquakes between 6.0 to 7.0 or higher on the Richter scale. The Almanor fault zone also remains seismically active, potentially capable of producing a mid-7.0 magnitude earthquake.

Despite the interconnectedness of volcanic activity and earthquakes in the region, predicting when an earthquake might trigger an eruption, or vice versa, remains elusive. The potential danger of an earthquake around 7.0 or more could result in significant volcanic activity. Residents of the area surrounding Lassen Volcanic National Park should stay prepared for the worst case scenario, as the area may be overdue for the next “big one.”