Each year, 1,000 to 3,000 earthquakes occur within Yellowstone National Park and its immediate surroundings. Although most are too small to be felt, these quakes reflect the active nature of the Yellowstone region, one of the most seismically active areas in the United States. Each year, several quakes of magnitude 3 to 4 are felt by people in the park.
Although some quakes are caused by rising magma and hot-ground-water movement, many emanate from regional faults related to crustal stretching and mountain building. For example, major faults along the Teton, Madison, and Gallatin Ranges pass through the park and likely existed long before the beginning of volcanism there. Movements along many of these faults are capable of producing significant earthquakes. The most notable earthquake in Yellowstone’s recent history occurred in 1959. Centered near Hebgen Lake, just west of the park, it had a magnitude of 7.5. This quake caused $11 million in damage (equivalent to $70 million in 2005 dollars) and killed 28 people, most of them in a landslide that was triggered by the quake.
Geologists conclude that large earthquakes like the Hebgen Lake event are unlikely within the Yellowstone Caldera itself, because subsurface temperatures there are high, weakening the bedrock and making it less able to rupture. However, quakes within the caldera can be as large as magnitude 6.5. A quake of about this size that occurred in 1975 near Norris Geyser Basin was felt throughout the region.
Even distant earthquakes can affect Yellowstone. In November 2002, the magnitude 7.9 Denali Fault earthquake struck central Alaska, 1,250 miles (2,000 km) northwest of Yellowstone. Because this quake’s energy was focused toward the active Yellowstone volcanic and hydrothermal system, it triggered hundreds of small earthquakes there. The region’s hydrothermal system is highly sensitive to quakes and undergoes significant changes in their wake. Earthquakes may have the potential to cause Yellowstone’s hot-water system to destabilize and produce explosive hydrothermal eruptions.
The above text is from the USGS website.
The routine earthquake activity in the Yellowstone region is at relatively low background levels. See below for current earthquake activity in the Yellowstone region.
Text Listing of Recent Yellowstone Earthquakes (From University of Utah)