With the news focusing on hurricanes, floods and wildfires something in Idaho is going under the news radar. New swarms in Idaho are setting records for active swarms this year in two different area of Idaho. The first swarm has been happening in the Yellow Plateau Caldera. The Yellowstone Caldera or supervolcano is fairly common knowledge, what is not common knowledge is that Yellowstone is not alone. There are actually 7 active calderas in the region and a second caldera is acting up. Last week I travelled to the area for a work matter and felt a few of the earthquakes myself. Also out of interest, this area was near the total eclipse zone a month back. Correlation?
On the edge of the Picabo Caldera is Soda Spring Idaho and the area has caused the USGS to do something that they generally don't do. They are issuing a detailed earthquake forecast for the region. Swarms are not uncommon for areas along faults and the Yellowstone region. Aftershock earthquakes are also common what is not common is predicting a greater earthquake from a long series of smaller earthquakes in a very active swarm.
Concerning Soda Springs the USGS says:
When there are more earthquakes, the chance of a large earthquake is greater, which means that the chance of damage is greater. Idaho and Montana experience earthquakes. While earthquakes are not that common, it is also not surprising to see earthquakes in these areas.
The USGS follow predicting one of three scenarios with probability outcomes:
Scenario #1 (most likely: 80-90% chance): The sequence will continue to decay over the next week, which means there will be fewer earthquakes. Earthquakes above M3 may be felt by those in the area, and occasional spikes in activity may be accompanied by additional M4-M5 earthquakes. While all earthquake sequences decay over time, there are several other possible outcomes, which are listed next.
Scenario #2 (less likely than Scenario #1 but possible with 10-20% chance): A similar sized or larger earthquake than the M5.3 mainshock may occur. This situation is often referred to as a “doublet” when a similar sized earthquake follows the original earthquake that kicked off the sequence. Doublets have occurred in places around the world, but they are not very common.
Scenario #3 (the least likely scenario but still possible with less than 1% chance): A much larger earthquake than M5.3 could occur, up to and including the M7.0 range, in which case we would call what has happened prior to any larger earthquake a foreshock sequence. We have seen this happen in other places around the world, with the most notable being L’Aquila, Italy in 2009. It is important to understand that this is a highly unlikely scenario, but we cannot ignore the possibility of this occurring. 