Location
2009/10/09 22:13:54 35.9630 -114.5460 11.0 3.90 Arizona
Arrival Times (from USGS)
Arrival time list
Felt Map
USGS Felt map for this earthquake
USGS Felt reports main page
Focal Mechanism
USGS/SLU Moment Tensor Solution
ENS 2009/10/09 22:13:54:0 35.96 -114.55 11.0 3.9 Arizona
Stations used:
BK.CMB CI.GLA CI.GSC CI.ISA CI.LDF II.PFO IU.TUC TA.R11A
TA.U20A TA.V20A TA.W18A TA.Y12C US.DUG
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
br c 0.12 0.25 n 4 p 2
Best Fitting Double Couple
Mo = 1.95e+21 dyne-cm
Mw = 3.46
Z = 9 km
Plane Strike Dip Rake
NP1 105 85 20
NP2 13 70 175
Principal Axes:
Axis Value Plunge Azimuth
T 1.95e+21 18 331
N 0.00e+00 69 118
P -1.95e+21 10 237
Moment Tensor: (dyne-cm)
Component Value
Mxx 8.05e+20
Mxy -1.61e+21
Mxz 6.76e+20
Myy -9.20e+20
Myz 1.57e+19
Mzz 1.16e+20
############--
# #############-----
#### T #############--------
##### #############---------
#######################-----------
########################------------
#########################-------------
##########################--------------
--########################--------------
-------####################---------------
-------------#############----------------
--------------------######----------------
--------------------------#---------------
------------------------###########-----
-----------------------#################
-- -----------------################
- P ----------------################
---------------################
---------------###############
-------------###############
---------#############
---###########
Global CMT Convention Moment Tensor:
R T P
1.16e+20 6.76e+20 -1.57e+19
6.76e+20 8.05e+20 1.61e+21
-1.57e+19 1.61e+21 -9.20e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20091009221354/index.html
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Preferred Solution
The preferred solution from an analysis of the surface-wave spectral amplitude radiation pattern, waveform inversion and first motion observations is
STK = 105
DIP = 85
RAKE = 20
MW = 3.46
HS = 9.0
The waveform inversion is preferred.
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
UNR |
USGS/SLU Moment Tensor Solution
ENS 2009/10/09 22:13:54:0 35.96 -114.55 11.0 3.9 Arizona
Stations used:
BK.CMB CI.GLA CI.GSC CI.ISA CI.LDF II.PFO IU.TUC TA.R11A
TA.U20A TA.V20A TA.W18A TA.Y12C US.DUG
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
br c 0.12 0.25 n 4 p 2
Best Fitting Double Couple
Mo = 1.95e+21 dyne-cm
Mw = 3.46
Z = 9 km
Plane Strike Dip Rake
NP1 105 85 20
NP2 13 70 175
Principal Axes:
Axis Value Plunge Azimuth
T 1.95e+21 18 331
N 0.00e+00 69 118
P -1.95e+21 10 237
Moment Tensor: (dyne-cm)
Component Value
Mxx 8.05e+20
Mxy -1.61e+21
Mxz 6.76e+20
Myy -9.20e+20
Myz 1.57e+19
Mzz 1.16e+20
############--
# #############-----
#### T #############--------
##### #############---------
#######################-----------
########################------------
#########################-------------
##########################--------------
--########################--------------
-------####################---------------
-------------#############----------------
--------------------######----------------
--------------------------#---------------
------------------------###########-----
-----------------------#################
-- -----------------################
- P ----------------################
---------------################
---------------###############
-------------###############
---------#############
---###########
Global CMT Convention Moment Tensor:
R T P
1.16e+20 6.76e+20 -1.57e+19
6.76e+20 8.05e+20 1.61e+21
-1.57e+19 1.61e+21 -9.20e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20091009221354/index.html
|
University of Nevada Reno Moment Tenor Solution
Locl Magnitude 3.9 - local magnitude (ML)
Moment Magnitude 3.49 - (Mw)
Event Location Google Map 39.963 -114.546
Friday, October 9, 2009 at 3:13:54 PM (PDT)
Friday, October 9, 2009 at 22:13:54.18 (UTC)
31 km from Boulder City, NV (19 miles) Azimuth E (85 degrees)
61 km from Las Vegas, NV (41 miles) Azimuth ESE (113 degrees)
Event ID: 294871
Map: Event Station Geometry
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Best Fit Solution
Event ID: 294871
Date: 2009/10/09,22:13:54
Waveform Fits
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Seismic Moment Tensor Solution
2009/10/09 (282) 22:13:52.00 35.9628 -114.5455 684215
Depth = 8.0 (km)
Mw = 3.49
Mo = 2.12x10^21 (dyne x cm)
Percent Double Couple = 90 %
Percent CLVD = 10 %
no ISO calculated
Epsilon=0.05
Percent Variance Reduction = 60.01 %
Total Fit = 5.34
Major Double Couple
strike dip rake
Nodal Plane 1: 18 74 -178
Nodal Plane 2: 288 89 -16
DEVIATORIC MOMENT TENSOR
Moment Tensor Elements: Spherical Coordinates
Mrr= 0.07 Mtt= 1.14 Mff= -1.21
Mrt= 0.53 Mrf= -0.27 Mtf= 1.65 EXP=21
Moment Tensor Elements: Cartesian Coordinates
1.14 -1.65 0.53
-1.65 -1.21 0.27
0.53 0.27 0.07
Eigenvalues:
T-axis eigenvalue= 2.06
N-axis eigenvalue= 0.11
P-axis eigenvalue= -2.17
Eigenvalues and eigenvectors of the Major Double Couple:
T-axis ev= 2.06 trend=334 plunge=10
N-axis ev= 0.00 trend=102 plunge=74
P-axis ev=-2.06 trend=242 plunge=12
Maximum Azmuithal Gap=243 Distance to Nearest Station=165.7 (km)
Number of Stations (D=Displacement/V=Velocity) Used=4 (defining only)
GMR.CI.D PDM.CI.D FUR.CI.D Y12C.TA.D
################-
T ##################-----
# ##################-------
########################---------
#########################----------
##########################-----------
-###########################-------------
############################-------------
-###########################---------------
------######################---------------
-----------################----------------
-----------------##########----------------
----------------------#######--------------
------------------------##########---------
------------------------###############----
-----------------------####################
--------------------####################
P -------------------#####################
------------------#####################
----------------####################
-------------####################
----------###################
------###################
-#################
#
All Stations defining and nondefining:
Station.Net Def Distance Azi Bazi lo-f hi-f vmodel
(km) (deg) (deg) (Hz) (Hz)
GMR.CI (D) Y 165.7 218 37 0.020 0.080 GMR.CI.wus.glib
PDM.CI (D) Y 188.4 169 349 0.020 0.080 PDM.CI.wus.glib
FUR.CI (D) Y 215.0 286 105 0.020 0.080 FUR.CI.wus.glib
Y12C.TA (D) Y 245.9 179 359 0.020 0.080 Y12C.TA.wus.glib
(V)-velocity (D)-Displacement
Author: ken (Gene Inchinose MTINV Moment Tensor Solution Package)
Date: 2009/10/10 03:35:47
mtinv Version 2.1_DEVEL OCT2008
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Velocity Model: Western US Ritsema and Lay 1995 JGR.
Z P QP S QS rho
4.00 4.52 500.00 2.61 250.00 2.39
28.00 6.21 500.00 3.59 250.00 2.76
20.00 7.73 1000.00 4.34 500.00 3.22
700.00 7.64 1000.00 4.29 500.00 3.19
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Waveform Inversion
The focal mechanism was determined using broadband seismic waveforms. The location of the event and the
and stations used for the waveform inversion are shown in the next figure.
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Location of broadband stations used for waveform inversion
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The program wvfgrd96 was used with good traces observed at short distance to determine the focal mechanism, depth and seismic moment. This technique requires a high quality signal and well determined velocity model for the Green functions. To the extent that these are the quality data, this type of mechanism should be preferred over the radiation pattern technique which requires the separate step of defining the pressure and tension quadrants and the correct strike.
The observed and predicted traces are filtered using the following gsac commands:
hp c 0.02 n 3
lp c 0.10 n 3
br c 0.12 0.25 n 4 p 2
The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 275 70 -10 3.09 0.2061
WVFGRD96 1.0 95 90 0 3.13 0.2319
WVFGRD96 2.0 100 80 -10 3.26 0.3490
WVFGRD96 3.0 105 90 5 3.30 0.3919
WVFGRD96 4.0 285 90 -10 3.33 0.4148
WVFGRD96 5.0 285 90 -15 3.37 0.4291
WVFGRD96 6.0 105 85 20 3.40 0.4407
WVFGRD96 7.0 105 85 20 3.42 0.4473
WVFGRD96 8.0 105 85 20 3.44 0.4520
WVFGRD96 9.0 105 85 20 3.46 0.4531
WVFGRD96 10.0 105 85 20 3.47 0.4530
WVFGRD96 11.0 105 85 20 3.49 0.4517
WVFGRD96 12.0 105 85 15 3.50 0.4498
WVFGRD96 13.0 105 90 15 3.51 0.4487
WVFGRD96 14.0 105 90 15 3.52 0.4468
WVFGRD96 15.0 105 90 15 3.53 0.4445
WVFGRD96 16.0 105 90 15 3.54 0.4414
WVFGRD96 17.0 285 90 -15 3.55 0.4374
WVFGRD96 18.0 285 85 -15 3.56 0.4335
WVFGRD96 19.0 285 85 -15 3.57 0.4298
WVFGRD96 20.0 285 70 10 3.58 0.4249
WVFGRD96 21.0 285 75 10 3.59 0.4212
WVFGRD96 22.0 285 75 10 3.60 0.4165
WVFGRD96 23.0 285 75 10 3.60 0.4110
WVFGRD96 24.0 285 70 10 3.61 0.4050
WVFGRD96 25.0 285 70 10 3.62 0.3993
WVFGRD96 26.0 285 70 10 3.63 0.3924
WVFGRD96 27.0 285 70 10 3.63 0.3845
WVFGRD96 28.0 290 65 15 3.64 0.3770
WVFGRD96 29.0 285 70 15 3.65 0.3692
The best solution is
WVFGRD96 9.0 105 85 20 3.46 0.4531
The mechanism correspond to the best fit is
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Figure 1. Waveform inversion focal mechanism
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The best fit as a function of depth is given in the following figure:
|
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Figure 2. Depth sensitivity for waveform mechanism
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The comparison of the observed and predicted waveforms is given in the next figure. The red traces are the observed and the blue are the predicted.
Each observed-predicted componnet is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. The number in black at the rightr of each predicted traces it the time shift required for maximum correlation between the observed and predicted traces. This time shift is required because the synthetics are not computed at exactly the same distance as the observed and because the velocity model used in the predictions may not be perfect.
A positive time shift indicates that the prediction is too fast and should be delayed to match the observed trace (shift to the right in this figure). A negative value indicates that the prediction is too slow.
The bandpass filter used in the processing and for the display was
hp c 0.02 n 3
lp c 0.10 n 3
br c 0.12 0.25 n 4 p 2
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Figure 3. Waveform comparison for selected depth
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Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to thewavefroms.
Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure.
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Discussion
The Future
Should the national backbone of the
USGS Advanced National Seismic System (ANSS)
be implemented with an interstation separation of 300 km, it is very likely that
an earthquake such as this would have been recorded at distances on the order of
100-200 km. This means that the closest station would have information on
source depth and mechanism that was lacking here.
Acknowledgements
Dr. Harley Benz, USGS, provided the USGS USNSN digital data.
The digital data used in this study were provided by Natural Resources Canada through their AUTODRM site http://www.seismo.nrcan.gc.ca/nwfa/autodrm/autodrm_req_e.php, and IRIS using their BUD interface.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint L ouis University, Universityof Memphis, Lamont Doehrty Earth Observatory, Boston College, the Iris stations and the Transportable Array of EarthScope.
Velocity Model
The WUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01
Model after 8 iterations
ISOTROPIC
KGS
FLAT EARTH
1-D
CONSTANT VELOCITY
LINE08
LINE09
LINE10
LINE11
H(KM) VP(KM/S) VS(KM/S) RHO(GM/CC) QP QS ETAP ETAS FREFP FREFS
1.9000 3.4065 2.0089 2.2150 0.302E-02 0.679E-02 0.00 0.00 1.00 1.00
6.1000 5.5445 3.2953 2.6089 0.349E-02 0.784E-02 0.00 0.00 1.00 1.00
13.0000 6.2708 3.7396 2.7812 0.212E-02 0.476E-02 0.00 0.00 1.00 1.00
19.0000 6.4075 3.7680 2.8223 0.111E-02 0.249E-02 0.00 0.00 1.00 1.00
0.0000 7.9000 4.6200 3.2760 0.164E-10 0.370E-10 0.00 0.00 1.00 1.00
Quality Control
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files:
DATE=Sun Oct 11 09:22:11 CDT 2009
Last Changed 2009/10/09