Source Parameter Search
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, Harvard, or Others. One or more more data sources may be selected. The default is all sources.
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 Harvard
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.
Harvard selects data contributed from the Harvard Seismology Group, Harvard University.
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 selects data from other contributors, such as the University of California, Berkeley (BRK), and the Laboratoire de Geophysique, Papeete, French Polynesia (PPT),
