USGS earthquake information mechanisms are all triggered by the same system, so they all receive the information at the same time. The time it takes for the system to receive the information primarily depends on the size and location of the earthquake:
An earthquake in California is processed and posted to the system in 2.5 minutes (on average). This is because our seismic network is very extensive in California, where there are many earthquakes and many people.
An earthquake in the U.S. outside of California (where seismic networks are not as dense), is typically posted within 8 minutes.
An earthquake outside the United States, where the seismic network is sparse in some areas, takes 20 minutes (on average) to process and post. Our webpages with realtime information are cached for 60 seconds, so there might be an additional delay of up to 60 seconds for the webpage to be updated.
From the time each system receives the information to the time you receive the information is the same for all systems, usually within a few seconds (unless there are network problems), except for the Earthquake Notification System (ENS) and the earthquake feeds, which can vary.
Since ENS has many thousands of accounts, all customized to receive different notifications, the time between ENS receiving the information and you receiving your notification can vary quite a bit. A large earthquake that generates many notifications might take up to 45 minutes to reach the last account on the list. A small earthquake that generates fewer notifications will take only a matter of several minutes to reach all accounts. The time it takes for the notifications to be sent depends on the capacity of the machines that send the email.
Social media outlets, such as Twitter, might be able to broadcast the occurrence of an earthquake faster than the USGS can using our standard mechanisms, but they cannot provide any quantitative data such as location and magnitude.
For the various Feeds, we cache different feeds for different lengths of time, so it depends on the feed you access. We try to balance data volume, how often the data in the feeds change, and server load so:
- GeoJSON 7-days and less feeds are cached for 1 minute
- Other 7-day and less feeds are cached for 5 minutes
- 30-day feeds and searches are cached for 15 minutes
- Event pages (and geojson detail feeds) are cached for 1 minute for the first 7 days after an event, and for 15 minutes after that
The Earthquake Map/List/Search interface uses GeoJSON feeds.