Source Parameter Search

Focal Mechanism Icon Data Source

If the selected source(s) is associated with an event, and this event also satifies all of the other search criteria, then the event will be selected for output.

Select from USGS, Global CMT, or, Others. One or more more data sources may be selected. The default is all sources.

USGS

USGS selects data from the USGS National Earthquake Information Center.

USGS Moment Tensor Solutions

Data are available starting January 1980.
These solutions have been determined using the body-wave moment tensor inversion method developed by Sipkin (1982). Globally distributed seismograph stations are used with distances between approximately 30 and 95 degrees that have suitable P waveforms. Only long-period vertical components are used. The source depth used is the depth that gives the smallest normalized mean-squared-error. Depth is the only hypocentral parameter determined since the inversion procedure is insensitive to small errors in both epicenter and origin time.

USGS Radiated Energy

Data are available starting November 1986.
The energy radiated by an earthquake is estimated from the energy spectral density of the broadband P waves, using the method described by Boatwright and Choy (1986), where the energy flux in the P waves is integrated directly. No correction for source directivity or frequency-dependent interference of the depth phases is incorporated into these estimates of radiated energy. Data used are either direct P waves (for deep earthquakes) or the P wave group consisting of P, pP and sP (for shallow earthquakes) from globally distributed seismograph stations that contribute digital data to the NEIC within two months of the occurrence of an event. The data are processed using the method of Harvey and Choy (1982) so that they are flat to velocity from low frequencies (generally 0.01 Hz) to at least 2.0 Hz. The affect of attenuation is corrected with the frequency-dependent t* of Choy and Cormier (1986). The focal mechanism used is either the P-wave first motion solution (F), the USGS moment tensor solution (M) or the Global centroid solution (C).

USGS Fault Plane Solutions

Data are available starting January 1980.
Beginning January 1996, the fault plane solution is determined primarily from least-squares fitting of synthetic waveforms and broadband body waves that are flat to displacement between approximately 0.01 to 5.0 Hz. The fault plane solution derived from broadband data is sensitive to the dynamic or high frequency part of the earthquake. Prior to January 1996, fault plane solutions were constrained primarily by using first motions from P, pP and PKP waves. Polarities were also obtained by using broadband displacement records of surface-reflected body waves (e.g., pP and sP), Hilbert-transformed body waves of certain secondary arrivals (e.g., PP), and transversely polarized S waves.

Global CMT

Global CMT selects data contributed from the Lamont-Doherty Seismology Group.

Centroid, Moment Tensor

Data are available starting January 1977.
These solutions have been determined using the long period body and mantle wave moment tensor inversion method described by Dziewonski, et.al. (1981) considering corrections due to an aspherical earth structure of model SH8/U4L8 (Dziewonski and Woodward, 1991).

Currently GSN, IDA/IRIS data are used. Long-period body waves and mantle waves are used. Mantle waves are routinely used in inversion for sources with moments greater than 5*10**18 Newton-meters (Nm).

See the Global CMT Catalog Search and the Harvard Seismology Home Page.

Others

Others selects data from other contributors, such as the University of California, Berkeley (BRK), and the Laboratoire de Geophysique, Papeete, French Polynesia (PPT),