The Advanced National Seismic System (ANSS) is a collaboration of the U.S. Geological Survey (USGS) and regional, state, and academic partners that collects and analyzes data on significant earthquakes to provide near real-time (generally within 10 to 30 minutes [1] ) information to emergency responders and officials, the news media, and the public. [2] Such information is used to anticipate the likely severity and extent of damage, and to guide decisions on the responses needed. [3]
Data is collected by eleven regional seismic networks and the National Seismic Network ("ANSS backbone") of dedicated stations, with additional inputs from overseas seismic networks. Analysis is done at the regional data centers, and at the USGS National Earthquake Information Center (NEIC), [4] with the results posted at the USGS earthquake web page (https://earthquake.usgs.gov/earthquakes/).
The National Strong Motion Project of the ANSS has instrumented 168 structures to record their response to very strong shaking. This data is used in research on earthquake-resistant engineering. [5]
The ANSS provides a range of products and services: [6]
These can be accessed at the USGS Earthquake page: https://earthquake.usgs.gov/earthquakes/.
As of 2023 the following networks were participating in the ANSS: [7]
Additional stations are operated by the USGS Albuquerque Seismological Laboratory (ASL).
The regional networks are deemed authoritative for the location and magnitude of earthquakes in their region. The NEIC receives additional data from about 3,000 stations around the world, and provides backup if a regional network is unable to communicate.
The Modified Mercalli intensity scale measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake.
The Pacific Northwest Seismic Network, or PNSN, collects and studies ground motions from about 400 seismometers in the U.S. states of Oregon and Washington. PNSN monitors volcanic and tectonic activity, gives advice and information to the public and policy makers, and works to mitigate earthquake hazard.
The National Earthquake Information Center is part of the United States Geological Survey (USGS) located on the campus of the Colorado School of Mines in Golden, Colorado. The NEIC has three main missions:
The EarthScope project was an National Science Foundation (NSF) funded earth science program that, from 2003-2018, used geological and geophysical techniques to explore the structure and evolution of the North American continent and to understand the processes controlling earthquakes and volcanoes. The project had three components: USArray, the Plate Boundary Observatory, and the San Andreas Fault Observatory at Depth. Organizations associated with the project included UNAVCO, the Incorporated Research Institutions for Seismology (IRIS), Stanford University, the United States Geological Survey (USGS) and National Aeronautics and Space Administration (NASA). Several international organizations also contributed to the initiative. EarthScope data are publicly accessible.
USArray is one of the three components of the Earthscope project [the other two being the Plate Boundary Observatory (PBO) and the San Andreas Fault Observatory at Depth (SAFOD)], funded by the National Science Foundation and being constructed, operated, and maintained as a collaborative effort with UNAVCO Inc., the Incorporated Research Institutions for Seismology (IRIS), and Stanford University, with contributions from several other national and international organizations. A major goal of USArray is to collect detailed seismic images of the North American lithosphere. The data collected from USArray will be integrated with geologic observations made on the earth's surface to help determine the geologic history of North America, as well as to better understand that geologic processes that are at work today. USArray consists of four "observatories":
Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram. Magnitude scales vary on what aspect of the seismic waves are measured and how they are measured. Different magnitude scales are necessary because of differences in earthquakes, the information available, and the purposes for which the magnitudes are used.
An earthquake warning system or earthquake alarm system is a system of accelerometers, seismometers, communication, computers, and alarms that is devised for notifying adjoining regions of a substantial earthquake while it is in progress. This is not the same as earthquake prediction, which is currently incapable of producing decisive event warnings.
Susan Elizabeth Hough is a seismologist at the United States Geological Survey in Pasadena, California, and scientist in charge of the office. She has served as an editor and contributor for many journals and is a contributing editor to Geotimes Magazine. She is the author of five books, including Earthshaking Science (Princeton).
The 2008 Illinois earthquake was one of the largest earthquakes ever recorded in the Midwest state of Illinois. This moderate strike-slip shock measured 5.2 on the moment magnitude scale and had a maximum Mercalli intensity of VII (Very strong). It occurred at 04:36:59 local time on April 18 near Bellmont and Mount Carmel, Illinois, within the Wabash Valley Seismic Zone. Earthquakes in this part of the country are often felt at great distances.
The 1868 Hayward earthquake occurred in the San Francisco Bay Area, California, United States on October 21. With an estimated moment magnitude of 6.3–6.7 and a maximum Mercalli intensity of IX (Violent), it was the most recent large earthquake to occur on the Hayward Fault Zone. It caused significant damage and a number of deaths throughout the region, and was known as the "Great San Francisco earthquake" prior to the 1906 San Francisco earthquake and fire.
The 1965 Puget Sound earthquake occurred at 08:28 AM PDT on April 29 within the Puget Sound region of Washington state. It had a magnitude of 6.7 on the moment magnitude scale and a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale. It caused the deaths of seven people and about $12.5–28 million in damage. There were no recorded aftershocks.
The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the United States government whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on March 3, 1879, to study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The agency also makes maps of extraterrestrial planets and moons based on data from U.S. space probes.
On May 4, 2018, an earthquake with a magnitude of Mw 6.9 struck Hawaii island in the Hawaii archipelago at around 12:33 p.m. local time. The earthquake's epicenter was near the south flank of Kīlauea, which has been the site of seismic and volcanic activity since late April of that year. According to the United States Geological Survey the quake was related to the new lava outbreaks at the volcano, and it resulted in the Hilina Slump moving about two feet. It was the largest earthquake to affect Hawaii since the 1975 earthquake, which affected the same region, killing two people and injuring another 28.
The Valparaíso earthquake of April 2017 was a strong earthquake that shook the cities of Valparaíso and Santiago on Monday, April 24, 2017, at 18:38 local time. Its epicenter was located off the coast of the Valparaíso Region and had a magnitude of 6.9 Mw. On the scale of Mercalli, the earthquake reached an intensity of VII.
The 2019 Ridgecrest earthquakes of July 4 and 5 occurred north and northeast of the town of Ridgecrest, California located in Kern County and west of Searles Valley. They included three initial main shocks of Mw magnitudes 6.4, 5.4, and 7.1, and many perceptible aftershocks, mainly within the area of the Naval Air Weapons Station China Lake. Eleven months later, a Mw 5.5 aftershock took place to the east of Ridgecrest. The first main shock occurred on Thursday, July 4 at 10:33 a.m. PDT, approximately 18 km (11.2 mi) ENE of Ridgecrest, and 13 km (8.1 mi) WSW of Trona, on a previously unnoticed NE-SW trending fault where it intersects the NW-SE trending Little Lake Fault Zone. This quake was preceded by several smaller earthquakes, and was followed by more than 1,400 detected aftershocks. The M 5.4 and M 7.1 quakes struck on Friday, July 5 at 4:08 a.m. and 8:19 p.m. PDT approximately 10 km (6 miles) to the northwest. The latter, now considered the mainshock, was the most powerful earthquake to occur in the state in 20 years. Subsequent aftershocks extended approximately 50 km (~30 miles) along the Little Lake Fault Zone.
The 2020 Central Idaho earthquake occurred in the western United States on March 31, 2020, at 5:52 PM MDT, near Ruffneck Peak in the Sawtooth Mountains of central Idaho, 72 miles (116 km) northeast of Boise and 19 miles (31 km) northwest of Stanley. It had a magnitude of 6.5 and was felt with a maximum intensity of VIII.
In 1954, the state of Nevada was struck by a series of earthquakes that began with three magnitude 6.0+ events in July and August that preceded the Mw 7.1–7.3 mainshock and M 6.9 aftershock, both on December 12. All five earthquakes are among the largest in the state, and the largest since the Cedar Mountain earthquake of 1932 and Pleasant Valley event in 1915. The earthquake was felt throughout much of the western United States.
David Jay Wald is a seismologist with the U.S. Geological Survey (USGS) at the National Earthquake Information Center (NEIC) in Golden, Colorado. He is an affiliated faculty member at the Colorado School of Mines, and served as the editor-in-chief of the Earthquake Engineering Research Institute's (EERI) journal, Earthquake Spectra, from 2018–2022. He also served on the Southern California Earthquake Center Science Planning Committee, 2014–2020.
Kate E. Allstadt is a geologist and seismologist employed by the U.S. Geological Survey (USGS) who works out of Golden, Colorado. She is a self-described "present-day geologist" for her interest in connections between geology of the Pacific Northwest and the people in its local communities. She is a published expert on the 2014 Oso landslide.