Outcrops of Obsidian Butte, California, near the Salton Sea.
A brief update on the two earthquake swarms making news right now:
Yellowstone The earthquake swarm at Yellowstone is still rumbling along, reaching over 1,000 earthquakes measured over the last week. However, the swarm has begun to die down overnight - with no earthquakes between 10:41 PM (MST) on 1/22 and 6 AM on 1/23. However, although this is a longer, bigger swarm than normal, it still isn't out of the regular rumblings at Yellowstone caldera. The USGS continues to say this swarm is tectonic, rather than magmatic or hydrothermal.
Bombay Beach/Obsidian Butte, California Another swarm that readers have pointed out is occurring at the south end of the Salton Sea in California. This should seem familiar as another swarm occurred there last year. This current swarm is occurring almost directly underneath Obsidian Butte - a favorite location for earthquake swarms in the area. Obsidian Butte is part of the Salton Buttes, a series of rhyolite domes that are ~16,000 years old. This area is a geothermal energy producer and there is extensive faulting as well, so more than likely, these earthquakes are tectonic or geothermal.
