Map showing location of major faults and offshore basins of the San Francisco area, from the study Vertical tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California.
How do you determine the place name for an earthquake?
For the automated naming of earthquakes we use a GeoNames dataset to reference populated places that are in close proximity to a seismic event. GeoNames has compiled a list of cities in the United States where the population is 1,000 or greater (cities1000.txt). This is the primary list that we use when selecting nearby places. In order to provide the public with a better understanding for the location of an event we try to list a variety of places in our nearby places list. This includes the closest known populated place in relation to the seismic event (which based on our dataset will have a population of 1,000 or greater), and the next 3 closest places that have a population of 10,000 or greater, and finally the closest capital city to the seismic event.
The reference point for the descriptive locations is usually either the City Hall of the town (or prominent intersection in the middle of town if there is no City Hall), but please refer to the GeoNames website for the most accurate information on their data.
If there is no nearby city within 300 kilometers (or if the nearby cities database is unavailable for some reason), the Flinn-Engdahl (F-E) seismic and geographical regionalization scheme is used. The boundaries of these regions are defined at one-degree intervals and therefore differ from irregular political boundaries. For example, F-E region 545 (Northern Italy) also includes small parts of France, Switzerland, Austria and Slovenia and F-E region 493 (Chesapeake Bay Region) includes all of the State of Delaware, plus parts of the District of Columbia, Maryland, New Jersey, Pennsylvania and Virginia. Beginning with January 2000, the 1995 revision to the F-E code has been used in the QED and PDE listings.
For large, significant earthquakes, we sometimes change the automated earthquake name to the popular name for which the earthquake has been commonly referred.
As an agency of the U.S. Government, we are expected to use the names and spellings approved by the U.S. Board on Geographic Names. Any requests to approve additional names should be made to the U.S. Board on Geographic Names.
Related
Does the Latest Earthquakes map show non-earthquake seismic events?
In addition to naturally occurring earthquakes, human activities such as mining and construction blasts can sometimes produce seismic waves large enough to be detected on the USGS national seismic network. These artificially-generated events have a different seismic ‘fingerprint’ from tectonic earthquakes, so they can be discerned by a seismologist when reviewed. Specifically, small quarry blasts...
What is UTC, and why do you report earthquakes in UTC?
UTC stands for Coordinated Universal Time, and for this purpose is the same as GMT (Greenwich Mean Time). Since the USGS and other seismic network agencies record earthquakes around the globe in all the various time zones, using a single standard time reference is best for record-keeping and exchange of data. The individual event pages with details about each earthquake use UTC for the reference...
Why do USGS earthquake magnitudes differ from those published by other agencies?
Magnitude estimates for a given earthquake can vary between reporting agencies due to differences in methodology, data availability, and inherent uncertainties in seismic data. Individual agencies use magnitude estimation procedures designed to meet the agency's specific needs and monitoring capabilities. Even for well-recorded events, differences in magnitude of 0.2 or 0.3 units are common and...
How quickly is earthquake information posted to the USGS website and sent out via the Earthquake Notification Service (ENS) and other feeds?
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...
Why/When does the USGS update the magnitude of an earthquake?
The USGS often updates an earthquake's magnitude in the hours and sometimes days following the event. Updates occur as more data become available for analysis and more time-intensive analysis is performed. Additional updates are possible as part of the standard procedure of assembling a final earthquake catalog. There are physical and operational constraints on how quickly seismic data are...
Why do some earthquakes disappear from the map/list?
The USGS and networks contributing to the Advance National Seismic System (ANSS) take great effort to provide accurate and timely earthquake information. Occasionally our systems produce erroneous information that is released to the public via our web pages or Earthquake Notification System. These mistakes are generally promptly identified by seismologists, removed from our web pages, and “delete”...
Why is the earthquake that was reported/recorded by network X, or that I felt, not on the Latest Earthquakes map/list?
The USGS Latest Earthquakes map and lists show events that have been located by the USGS and contributing agencies within the last 30 days. They should NOT be considered complete lists of all events in the U.S. and adjacent areas and especially should NOT be considered complete lists of all magnitude 4.5 and greater events that occur around the globe. In most cases, we locate and report an...
San Francisco area seismic fault map
Map showing location of major faults and offshore basins of the San Francisco area, from the study Vertical tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California.
Lassen Volcanic Center earthquake swarm of June 24, 2024
This map shows the location of the June 24, 2024 earthquake swarm at the Lassen Volcanic Center relative to Lassen Peak and Growler & Morgan Hot Springs. Earthquakes are indicated by white, blue, and yellow circles, scaled to the earthquake size.
This map shows the location of the June 24, 2024 earthquake swarm at the Lassen Volcanic Center relative to Lassen Peak and Growler & Morgan Hot Springs. Earthquakes are indicated by white, blue, and yellow circles, scaled to the earthquake size.
PubTalk 5/2021 - Where Earthquakes Hide in the Desert
Title: Where Earthquakes Hide in the Desert: What we've learned from recent fault ruptures in the western U.S.
By Austin J. Elliott, USGS Research Geologist
Title: Where Earthquakes Hide in the Desert: What we've learned from recent fault ruptures in the western U.S.
By Austin J. Elliott, USGS Research Geologist
Epicenter of the 1964 Alaska Earthquake map
Map of southern Alaska showing the epicenter of the 1964 Alaska Earthquake (red star).
Map of southern Alaska showing the epicenter of the 1964 Alaska Earthquake (red star).
Groundshaking animation: Hayward Fault, Oakland epicenter
Scenario shows the ground shaking for a magnitude 7.0 earthquake on the Hayward fault with the epicenter in Oakland, California. Visit M7.0 Earthquake Scenarios - Hayward Fault for detailed perspective views.
Scenario shows the ground shaking for a magnitude 7.0 earthquake on the Hayward fault with the epicenter in Oakland, California. Visit M7.0 Earthquake Scenarios - Hayward Fault for detailed perspective views.
Related
Does the Latest Earthquakes map show non-earthquake seismic events?
In addition to naturally occurring earthquakes, human activities such as mining and construction blasts can sometimes produce seismic waves large enough to be detected on the USGS national seismic network. These artificially-generated events have a different seismic ‘fingerprint’ from tectonic earthquakes, so they can be discerned by a seismologist when reviewed. Specifically, small quarry blasts...
What is UTC, and why do you report earthquakes in UTC?
UTC stands for Coordinated Universal Time, and for this purpose is the same as GMT (Greenwich Mean Time). Since the USGS and other seismic network agencies record earthquakes around the globe in all the various time zones, using a single standard time reference is best for record-keeping and exchange of data. The individual event pages with details about each earthquake use UTC for the reference...
Why do USGS earthquake magnitudes differ from those published by other agencies?
Magnitude estimates for a given earthquake can vary between reporting agencies due to differences in methodology, data availability, and inherent uncertainties in seismic data. Individual agencies use magnitude estimation procedures designed to meet the agency's specific needs and monitoring capabilities. Even for well-recorded events, differences in magnitude of 0.2 or 0.3 units are common and...
How quickly is earthquake information posted to the USGS website and sent out via the Earthquake Notification Service (ENS) and other feeds?
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...
Why/When does the USGS update the magnitude of an earthquake?
The USGS often updates an earthquake's magnitude in the hours and sometimes days following the event. Updates occur as more data become available for analysis and more time-intensive analysis is performed. Additional updates are possible as part of the standard procedure of assembling a final earthquake catalog. There are physical and operational constraints on how quickly seismic data are...
Why do some earthquakes disappear from the map/list?
The USGS and networks contributing to the Advance National Seismic System (ANSS) take great effort to provide accurate and timely earthquake information. Occasionally our systems produce erroneous information that is released to the public via our web pages or Earthquake Notification System. These mistakes are generally promptly identified by seismologists, removed from our web pages, and “delete”...
Why is the earthquake that was reported/recorded by network X, or that I felt, not on the Latest Earthquakes map/list?
The USGS Latest Earthquakes map and lists show events that have been located by the USGS and contributing agencies within the last 30 days. They should NOT be considered complete lists of all events in the U.S. and adjacent areas and especially should NOT be considered complete lists of all magnitude 4.5 and greater events that occur around the globe. In most cases, we locate and report an...
San Francisco area seismic fault map
Map showing location of major faults and offshore basins of the San Francisco area, from the study Vertical tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California.
Map showing location of major faults and offshore basins of the San Francisco area, from the study Vertical tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California.
Lassen Volcanic Center earthquake swarm of June 24, 2024
This map shows the location of the June 24, 2024 earthquake swarm at the Lassen Volcanic Center relative to Lassen Peak and Growler & Morgan Hot Springs. Earthquakes are indicated by white, blue, and yellow circles, scaled to the earthquake size.
This map shows the location of the June 24, 2024 earthquake swarm at the Lassen Volcanic Center relative to Lassen Peak and Growler & Morgan Hot Springs. Earthquakes are indicated by white, blue, and yellow circles, scaled to the earthquake size.
PubTalk 5/2021 - Where Earthquakes Hide in the Desert
Title: Where Earthquakes Hide in the Desert: What we've learned from recent fault ruptures in the western U.S.
By Austin J. Elliott, USGS Research Geologist
Title: Where Earthquakes Hide in the Desert: What we've learned from recent fault ruptures in the western U.S.
By Austin J. Elliott, USGS Research Geologist
Epicenter of the 1964 Alaska Earthquake map
Map of southern Alaska showing the epicenter of the 1964 Alaska Earthquake (red star).
Map of southern Alaska showing the epicenter of the 1964 Alaska Earthquake (red star).
Groundshaking animation: Hayward Fault, Oakland epicenter
Scenario shows the ground shaking for a magnitude 7.0 earthquake on the Hayward fault with the epicenter in Oakland, California. Visit M7.0 Earthquake Scenarios - Hayward Fault for detailed perspective views.
Scenario shows the ground shaking for a magnitude 7.0 earthquake on the Hayward fault with the epicenter in Oakland, California. Visit M7.0 Earthquake Scenarios - Hayward Fault for detailed perspective views.
Updated Date: September 10, 2024