The May 15, 2020 M 6.5 earthquake 56 km west f Tonopah, Nevada, occurred as the result of strike slip faulting in the shallow crust of the North America plate. Preliminary focal mechanism solutions for the event, which describe the style of faulting in an earthquake, indicate slip likely occurred on a steeply dipping fault striking either east-west (left-lateral) or north-south (right-lateral). This earthquake occurred within the Walker Lane, an active zone of seismicity roughly aligned with the California-Nevada border. Tectonically, the Walker Lane accommodates up to 25% of the North America:Pacific Plate motion, with the remainder mostly accommodated on the San Andreas fault system.
About two dozen M5+ earthquakes have occurred within 100 km of this event over the past 50 years, mostly to the west and south. Two M6+ events have occurred over the same region in the past century – a M 6.5 earthquake 40 km to the northwest in January 1934, and a M 6.8 event 50 km to the north in December 1932. Both of these earthquakes caused severe local shaking (MMI VIII); the 1932 earthquake is documented to have caused damage in the sparsely populated surrounding region. As of 12pm UTC, 6 M4+ aftershocks have occurred since the M 6.5 earthquake, extending over a region about 30 km to the west of the mainshock.
Be ready for more earthquakes
- More earthquakes than usual (called aftershocks) will continue to occur near the mainshock.
- When there are more earthquakes, the chance of a large earthquake is greater which means that the chance of damage is greater.
- The USGS advises everyone to be aware of the possibility of aftershocks, especially when in or around vulnerable structures such as unreinforced masonry buildings.
- This earthquake could be part of a sequence. An earthquake sequence may have larger and potentially damaging earthquakes in the future, so remember to: Drop, Cover, and Hold on.
What we [USGS] think will happen next
According to our forecast, over the next 1 Week there is a 4 % chance of one or more aftershocks that are larger than magnitude 6.5. It is likely that there will be smaller earthquakes over the next 1 Week, with 3 to 710 magnitude 3 or higher aftershocks. Magnitude 3 and above are large enough to be felt near the epicenter. The number of aftershocks will drop off over time, but a large aftershock can increase the numbers again, temporarily.
About this earthquake and related aftershocks
So far in this sequence there have been 23 magnitude 3 or higher earthquakes, which are strong enough to be felt, and 1 magnitude 5 or higher earthquakes, which are large enough to do damage.
Our detailed aftershock forecast
The USGS estimates the chance of more aftershocks as follows: Within the next 1 Week until 2020-05-22 13:10:00 (UTC):
- The chance of an earthquake of magnitude 3 or higher is > 99 %, and it is most likely that as few as 3 or as many as 710 such earthquakes may occur in the case that the sequence is re-invigorated by a larger aftershock.
- The chance of an earthquake of magnitude 5 or higher is 45 %, and it is most likely that as few as 0 or as many as 8 such earthquakes may occur.
- The chance of an earthquake of magnitude 6 or higher is 10 %, and it is most likely that as few as 0 or as many as 2 such earthquakes may occur.
- The chance of an earthquake of magnitude 7 or higher is 1 %, such an earthquake is possible but with a low probability.
About our earthquake forecasts
No one can predict the exact time or place of any earthquake, including aftershocks. Our earthquake forecasts give us an understanding of the chances of having more earthquakes within a given time period in the affected area. We calculate this earthquake forecast using a statistical analysis based on past earthquakes.
Our forecast changes as time passes due to decline in the frequency of aftershocks, larger aftershocks that may trigger further earthquakes, and changes in forecast modeling based on the data collected for this earthquake sequence.
This forecast was issued: 2020-05-15 13:03:27 (UTC)
This forecast will be updated on or before 2020-05-22 13:03:27 (UTC)
source: USGS Twitter feed