Moment tensor solutions

Moment tensor and seismicity plots

This web page describes the SLU regional moment tensors for the continental US and Canada. The techniques used are described in
Herrmann, R. B., H. Benz, and C. J. Ammon (2011). Monitoring the earthquake process in North America, Bull. Seism. Soc. Am. 01, 2609-2625, doi:10.1785/0120110095 .

Moment tensor maps

The following figures present the focal mechanisms tabulated below. The color red is use to represent focal mechanisms determined for the current year.

Useful links

World Stress Map Project https://www.world-stress-map.org/casmo

SLU Digital Data Focal Mechanism Page with Analysis Detail

SLU Moment Tensors in KMZ format for GoogleEarth Download as a file and then use GoogleEarth to open the file, or Download and start GoogleEarth automatically. If blue-white beach balls are overwritten by a box, go to the Temporary place menu and then to North America SLU/USGS Regional Moment Tensor Solutions and then uncheck and check that box and the folder beneath.

SLU North America Moment Tensor catalog in CSV format with TABS separating columns. This catalog consists of a header line followed by tab separated columns for each earthquake. The columns are Year, Month, Day, Hour, Minute, Second (UTC), Latitude, Longitude, moment tensor depth in km, Mw, Stk1, Dip1 Rake1 (plane 1), Stk2, Dip2, Rake2 (plane 2), P-axis trend, P-axis plunge, T-axis trend, T-axis plunge, Null-axis trend, Null-axis plunge, faulting type, reference, velocity model used, catalog authority and event ID. The reference is described at the bottom of this page. The symbols describing the regime are from Zoback (1992):
- NF - normal fault,
- SS - strike-slip fault,
- TF - thrust fault,
- NS - normal-strike slip oblique fault,
- TS - thrust-strike-clip oblique fault,
- XX - no clear determination of direction of maximum compressive stress.
The velocity model used is essential to obtaining the solution. The computations yielding the results cannot be duplicated unless the same velocity model is used. The velocity models used are given in the Computer Programs in Seismology 3.30 model96 format as follow:
- CUS model. This is used for the interior craton of North America.
- WUS model. This is used for western North America and the Gulf Coastal Plain.
- DU model. This is the velocity model used in the Du et al (2003) paper for earthquakes in the northeaster US and southeastern Canada.
- GSKAN model. tjhis was developed for events in southern Kansas
- HutchKS model. This was developed for events near Hutchinson, Kansas
- TTX model. This was developed for events near tipton, Texas. This was required because of the deep column of Gulf Coast sediments.
To distinguish this tabulation from other catalogs, the catalog authority is given in the last field, e.g., SLU for this catalog.

Useful scripts

The following scripts provide a simple way to access some information contained in this catalog. First download and save the catalog Mech.list .

DOCOUNT - this counts the numeber of moment tensors in this catalog by year. Download and save the shell script DOCOUNT. Then
```
chmod +x DOCOUNT

To run, just enter
DOCOUNT
```

DOSEARCH - search for moment tensors within a geographical region. Download and save the shell script DOSEARCH. then

chmod +x DOCOUNT

To run, just enter this to get the syntax:
DOSEARCH
Syntax: DOSEARCH Clat Clon Dlat Dlon

To search for events within the region bounded in latitude by Clat-Dlat and  Clat+Dlat 
and longitude by Clon-Dlon and Clon+Dlon. Note for the western hemisphere, 
the longitudes are negative. The columns are date_time, latitude,longitude, moment tensor depth, Mw, strike, dip, rake, source, velocity model, authority and event ID.

Example:

DOSEARCH 39 1 -90 2
19740403_230502 38.592 -88.094 15.0 4.34 310 70 0 JGR79 CUS SLU usp00005uz
20110607_081034 38.077 -90.902 27.0 3.86 100 80 25 WEB CUS SLU nm608924
20150530_004114 38.462 -88.356 22.0 3.33 155 60 5 WEB CUS SLU nm60008708
20170701_180732 38.850 -89.228 18.0 3.12 110 85 35 WEB CUS SLU nm60173557
20220429_223038 38.529 -90.500 9.0 2.74 290 75 10 WEB WUS SLU nm60392336

References

Code	Reference
BSSA80	Herrmann, R. B., J. Dewey and S.-K. Park (1980). The Dulce, New Mexico earthquakes of January, 1966 Bull. Seism. Soc. Am. 70, 2171-2183.
BSSA81	Herrmann, R. B., C. Y. Wang and S. -K. Park (1981). The Denver earthquakes of 1967-1968, Bull. Seism. Soc. Am. 71, 731-746.
BSSA81b	Eberhart-Phillips, D., R. M. Richardson, M. L. Sbar and R. B. Herrmann (1981). Analysis of the 4 February 1976 Chino Valley, Arizona Earthquake, Bull. Seism. Soc. Am. 71, 787-802.
BSSA82	Herrmann, R. B., C. A. Langston, and J. E. Zollweg (1982). The Sharpsburg, Kentucky earthquake of July 27, 1980, J. E. Zollweg ), Bull Seism. Soc. Am. 72, 1219-1239.
BSSA86	Herrmann, R. B. (1986). Surface-wave studies of some South Carolina earthquakes, Bull. Seism. Soc. Am. 76, 111-121.
DU	Du, Wen-xuan; Kim, Won-Young; Sykes, Lynn R. (2003). Earthquake Source Parameters and State of Stress for the Northeastern United States and Southeastern Canada from Analysis of Regional Seismograms, Bull. Seism. Soc. Am. 93, 1633 - 1648.
CHANG	Chang, T.-M. (1997). Evaluation of Surface-Wave Waveform Modeling for Lithosphere Velocity Structure, Ph.D. Disserations, Saint Louis University, PDF 3,167 kbytes ).
EQN80	Voss, J. A. and R. B. Herrmann (1980). A surface wave study of the June 16, 1978 Texas earthquake, Earthquake Notes 51, 3-14.
ENG97	Herrmann, R. B., and C. J. Ammon (1997). Faulting parameters of earthquakes in the New Madrid, Missouri region, Engineering Geology 46, 299-311.
JGR79	Herrmann, R. B. (1979). Surface wave focal mechanisms for eastern North American earthquakes with tectonic implications, J. Geophys. Res.84, 3543-3552.
SRL88	Schwartz, S. Y., and D. H. Christensen (1988). The 12 July St. Marys, Ohio earthquake and recent seismicity in the Anna, Ohio seismogenic zone, Seism. Res. Letters 59,, 57-62.
SRL89	Taylor, K. B., R. B. Herrmann, M. W. Hamburger, G. L. Pavlis, A. Johnston, C. Langer and C. Lam (1989). The southeastern Illinois earthquake of 10 June 1987, Seism. Res. Letters 60, 101-110.
SRL92	Nguyen, B. V., and R. B. Herrmann (1992). Determination of source parameters for central and eastern North American earthquakes (1982-1986), Seism. Res. Letters 63, 567-586.
SRL98	Ammon, C. J., R. B. Herrmann, C. A. Langston, and H. Benz (1998). Source parameters of the January 16, 1994 Wyomissing Hills, Pennsylvania earthquakes, Seism. Res. Letters 69, 261-269.
SRL00	Maceira, M., C. J. Ammon and R. B. Herrmann (2000). Faulting parameters of the September 25, 1998 Pymatuning, Pennsylvania earthquake, Seism. Res. Letters 71, 742-752.
tWEB	Not yet placed on the web page
WEB	SLU Digital Data Focal Mechanism Page

Moment tensor tabulation for 3341 earthquakes

The following file gives the focal mechanism information used to create the table shown above. This ASCII file has the following infomation in the columns: Event date, latitude, longitude, broadband depth, moment magnitude, strike, dip, rake, and citation. The citation is the same as that above. The relation between seismic moment, M₀ and moment magnitude M_w is log M₀ = 1.5 M_w + 16.05, where the seismic moment is in units of dyne-cm.

Mechanism tabulation

Magnitude Scales

A detailed compilation of ML and mLg is given in the link: Magnitude Study.

Last Changed "Thu May 1 12:45:27 UTC 2025"