24 articles
Advanced National Seismic System
The Advanced National Seismic System (ANSS) is a United States earthquake monitoring program led by the U.S. Geological Survey, coordinating regional networks since Congress endorsed it in 2000.
Array calibration
Array calibration is the family of methods that estimates and corrects errors in sensor position, timing, and gain and phase response across arrays of receivers.
b-value
The b-value is the slope parameter in the Gutenberg–Richter law, which relates earthquake counts to magnitude; typically 0.8 to 1.2, it measures the ratio of small to large earthquakes.
China Earthquake Networks Center
The China Earthquake Networks Center (中国地震台网中心) is the national institution of the China Earthquake Administration that operates China's seismic monitoring networks and issues rapid earthquake reports and early warnings.
Coda wave interferometry
Coda wave interferometry is a seismological and ultrasonic method, introduced in 2002, that detects small velocity changes by comparing multiply scattered coda waves, used to monitor volcanoes and faults.
Earthquake early warning
Earthquake early warning (EEW) detects an earthquake that has already begun and sends alerts giving people seconds to tens of seconds to take protective action before strong shaking arrives.
Earthquake location
Earthquake location is the seismological procedure that determines where and when an earthquake started, solving for the hypocenter's coordinates and origin time from arrival times recorded at many stations.
Earthquake swarms
An earthquake swarm is a sequence of many similar, mostly small earthquakes clustered in space and time without a mainshock, often driven by fluids or magma.
Global Seismographic Network
The Global Seismographic Network (GSN) is a global network of about 150 seismic stations, established in 1988, that records earthquakes and provides its data free in real time.
Horizontal-to-vertical spectral ratio
The horizontal-to-vertical spectral ratio (HVSR) is a single-station seismological method that estimates a site's fundamental resonance frequency from ambient vibration or earthquake recordings using one three-component seismometer.
International Federation of Digital Seismograph Networks
The International Federation of Digital Seismograph Networks (FDSN) is a global organization of seismograph network operators, founded in 1984, that coordinates station siting and open data exchange.
Machine learning earthquake detection
Machine learning earthquake detection uses trained neural networks to find earthquake signals in seismic recordings and pick P and S wave arrival times, replacing manual analysis.
Magnitude of completeness
The magnitude of completeness (Mc) is the lowest magnitude at which 100% of earthquakes in a region are reliably detected by a seismic network; below it, smaller quakes are missed.
Microseismic monitoring
Microseismic monitoring is a passive geophysics method that records very small earthquakes from hydraulic fracturing and fluid flow, used to image subsurface fractures and stress changes.
Moment tensor inversion
Moment tensor inversion is a seismological technique that estimates the forces at an earthquake source by fitting synthetic seismograms to waveforms, yielding fault orientation, seismic moment, and moment magnitude.
Pacific Northwest Seismic Network
The Pacific Northwest Seismic Network (PNSN), run by the University of Washington, monitors earthquakes and volcanoes across Washington and Oregon and feeds the USGS ShakeAlert early warning system.
Polarization analysis (seismology)
Polarization analysis in seismology characterizes the direction and shape of ground particle motion recorded by three-component seismic stations, supporting event detection, direction finding, and filtering.
Seismic moment
Seismic moment (symbol M0) is the physical quantity seismologists use to measure earthquake size: the product of rock rigidity, fault rupture area, and average slip.
Seismic network
A seismic network is a coordinated set of seismometers at distributed locations whose recordings are combined at a data center to detect, locate, and characterize earthquakes.
Seismic phase picking
Seismic phase picking is the task of determining the arrival times of P and S waves on seismograms, a prerequisite for earthquake location and early warning.
ShakeAlert
ShakeAlert is the USGS earthquake early warning system for the West Coast, detecting quakes that have already started and alerting people in California, Oregon, and Washington since 2019.
Shear wave splitting
Shear wave splitting is a seismological technique in which anisotropic rock splits a passing shear wave into two waves of different speed and polarization, revealing mantle deformation.
Southern California Seismic Network
The Southern California Seismic Network, operated jointly by Caltech and the U.S. Geological Survey, monitors earthquakes across southern California, keeping a continuous catalog of over 1,000,000 events since 1932.
USArray
USArray is a continental-scale seismic observatory and component of NSF's EarthScope program, funded in 2003 to record earthquakes and image the structure beneath North America with dense seismograph networks.