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9/17/2017 -- USGS issues EARTHQUAKE FORECAST for Soda Springs Idaho -- Science moves forward

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Published on Sep 17, 2017

USGS earthquake forecast for Soda Springs: Full text:

USGS earthquake forecast for Soda Springs: Full text: Earthquake Forecast The M5.3 Soda Springs Sequence is particularly active, producing more aftershocks on average than other earthquakes of this magnitude. In terms of future larger earthquakes in this area: 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. This sequence may have damaging earthquakes in the future, so remember to: Drop, Cover, and Hold on if you feel the ground shaking. Due to the active and ongoing nature of this sequence, we have developed an earthquake forecast for continuing seismicity. No one can predict the exact time or place of any earthquake, including aftershocks. What our earthquake forecasts do is give us an understanding of the chances of having more earthquakes within a given time period. We calculate this earthquake forecast using a statistical analysis based on past earthquakes in similar tectonic environments, as well as the aftershocks recorded to date for this sequence. Our forecast changes as time passes due to the decay in the frequency of aftershocks, larger aftershocks that reinvigorate the sequence, and changes in forecast modeling based on the earthquake data collected. Similar to weather models, our models will also change with more data and information.

The longer this sequence goes on, the more we learn about what it will do in the future. We have taken a detailed forecast and developed three scenarios that we consider to be the most likely. These scenarios are for the following week only, but earthquakes will continue to be possible at later times. We will update the forecast as more information becomes available. Here are the three scenarios or possibilities for the week starting Sept. 14, 2017, based on earthquake forecast models: 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. These probabilities will be updated periodically.