Location
2014/04/07 19:27:00 44.47 6.69 5.0 5.0 France
Arrival Times (from USGS)
Arrival time list
Felt Map
USGS Felt map for this earthquake
USGS Felt reports archive
Focal Mechanism
USGS/SLU Moment Tensor Solution
ENS 2014/04/07 19:27:00:0 44.47 6.69 5.0 5.0 France
Stations used:
CH.BALST CH.BERGE CH.BNALP CH.BOURR CH.BRANT CH.DAGMA
CH.DIX CH.EMBD CH.EMING CH.EMMET CH.FIESA CH.FUSIO CH.GIMEL
CH.GRIMS CH.HASLI CH.LAUCH CH.LLS CH.MMK CH.MUO CH.PANIX
CH.SENIN CH.SIMPL CH.SLE CH.SULZ CH.TORNY CH.VANNI CH.WALHA
CH.WILA CH.WIMIS CH.ZUR FR.ARBF FR.ARTF FR.ASEAF FR.BLAF
FR.BSTF FR.CALF FR.CFF FR.CHIF FR.CHMF FR.DOU FR.EILF
FR.ISO FR.LRVF FR.MLYF FR.MON FR.MONQ FR.OG02 FR.OG35
FR.OGDI FR.OGGM FR.OGMO FR.OGS1 FR.OGS2 FR.PYLO FR.RUSF
FR.SAOF FR.TERF FR.TRBF FR.TURF G.CLF G.ECH G.SSB GE.STU
GE.WLF GR.BFO GR.GRC2 GR.GRC3 GR.TMO22 GR.UBR GU.CARD
GU.CIRO GU.ENR GU.GBOS GU.LSD GU.MAIM GU.NEGI GU.PZZ
GU.REMY GU.ROTM GU.RRL GU.RSP GU.TRAV IV.DOI IV.FNVD
IV.MONC IV.MRGE IV.PLMA IV.QLNO MN.BNI RD.LOR RD.MTLF
RD.ORIF
Filtering commands used:
cut a -20 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.74e+23 dyne-cm
Mw = 4.76
Z = 11 km
Plane Strike Dip Rake
NP1 154 78 -144
NP2 55 55 -15
Principal Axes:
Axis Value Plunge Azimuth
T 1.74e+23 15 280
N 0.00e+00 52 170
P -1.74e+23 34 20
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.01e+23
Mxy -6.69e+22
Mxz -6.78e+22
Myy 1.43e+23
Myz -7.00e+22
Mzz -4.23e+22
--------------
##--------------------
#####-----------------------
#######----------- ---------
#########----------- P -----------
###########---------- -----------#
############------------------------##
##############----------------------####
# ##########---------------------#####
## T ###########-------------------#######
## ############-----------------########
##################---------------#########
###################------------###########
###################---------############
####################------##############
####################--################
##################--################
############--------##############
--------------------##########
--------------------########
-------------------###
--------------
Global CMT Convention Moment Tensor:
R T P
-4.23e+22 -6.78e+22 7.00e+22
-6.78e+22 -1.01e+23 6.69e+22
7.00e+22 6.69e+22 1.43e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20140407192700/index.html
|
Preferred Solution
The preferred solution from an analysis of the surface-wave spectral amplitude radiation pattern, waveform inversion and first motion observations is
STK = 55
DIP = 55
RAKE = -15
MW = 4.76
HS = 11.0
The NDK file is 20140407192700.ndk
The waveform inversion is preferred.
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
INGVTDMT |
USGS/SLU Moment Tensor Solution
ENS 2014/04/07 19:27:00:0 44.47 6.69 5.0 5.0 France
Stations used:
CH.BALST CH.BERGE CH.BNALP CH.BOURR CH.BRANT CH.DAGMA
CH.DIX CH.EMBD CH.EMING CH.EMMET CH.FIESA CH.FUSIO CH.GIMEL
CH.GRIMS CH.HASLI CH.LAUCH CH.LLS CH.MMK CH.MUO CH.PANIX
CH.SENIN CH.SIMPL CH.SLE CH.SULZ CH.TORNY CH.VANNI CH.WALHA
CH.WILA CH.WIMIS CH.ZUR FR.ARBF FR.ARTF FR.ASEAF FR.BLAF
FR.BSTF FR.CALF FR.CFF FR.CHIF FR.CHMF FR.DOU FR.EILF
FR.ISO FR.LRVF FR.MLYF FR.MON FR.MONQ FR.OG02 FR.OG35
FR.OGDI FR.OGGM FR.OGMO FR.OGS1 FR.OGS2 FR.PYLO FR.RUSF
FR.SAOF FR.TERF FR.TRBF FR.TURF G.CLF G.ECH G.SSB GE.STU
GE.WLF GR.BFO GR.GRC2 GR.GRC3 GR.TMO22 GR.UBR GU.CARD
GU.CIRO GU.ENR GU.GBOS GU.LSD GU.MAIM GU.NEGI GU.PZZ
GU.REMY GU.ROTM GU.RRL GU.RSP GU.TRAV IV.DOI IV.FNVD
IV.MONC IV.MRGE IV.PLMA IV.QLNO MN.BNI RD.LOR RD.MTLF
RD.ORIF
Filtering commands used:
cut a -20 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.74e+23 dyne-cm
Mw = 4.76
Z = 11 km
Plane Strike Dip Rake
NP1 154 78 -144
NP2 55 55 -15
Principal Axes:
Axis Value Plunge Azimuth
T 1.74e+23 15 280
N 0.00e+00 52 170
P -1.74e+23 34 20
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.01e+23
Mxy -6.69e+22
Mxz -6.78e+22
Myy 1.43e+23
Myz -7.00e+22
Mzz -4.23e+22
--------------
##--------------------
#####-----------------------
#######----------- ---------
#########----------- P -----------
###########---------- -----------#
############------------------------##
##############----------------------####
# ##########---------------------#####
## T ###########-------------------#######
## ############-----------------########
##################---------------#########
###################------------###########
###################---------############
####################------##############
####################--################
##################--################
############--------##############
--------------------##########
--------------------########
-------------------###
--------------
Global CMT Convention Moment Tensor:
R T P
-4.23e+22 -6.78e+22 7.00e+22
-6.78e+22 -1.01e+23 6.69e+22
7.00e+22 6.69e+22 1.43e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20140407192700/index.html
|
|
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.
|
|
Location of broadband stations used for waveform inversion
|
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:
cut a -20 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 60 85 5 4.37 0.3019
WVFGRD96 2.0 60 85 10 4.49 0.3916
WVFGRD96 3.0 50 50 -25 4.61 0.4353
WVFGRD96 4.0 50 45 -25 4.66 0.4865
WVFGRD96 5.0 50 45 -25 4.68 0.5265
WVFGRD96 6.0 50 45 -25 4.69 0.5547
WVFGRD96 7.0 50 50 -25 4.70 0.5746
WVFGRD96 8.0 50 45 -30 4.76 0.6054
WVFGRD96 9.0 50 50 -25 4.76 0.6113
WVFGRD96 10.0 50 50 -25 4.76 0.6143
WVFGRD96 11.0 55 55 -15 4.76 0.6147
WVFGRD96 12.0 55 55 -15 4.77 0.6146
WVFGRD96 13.0 55 55 -10 4.77 0.6120
WVFGRD96 14.0 55 55 -10 4.78 0.6085
WVFGRD96 15.0 55 55 -10 4.78 0.6039
WVFGRD96 16.0 55 60 -10 4.79 0.5983
WVFGRD96 17.0 60 60 5 4.79 0.5940
WVFGRD96 18.0 60 60 5 4.80 0.5898
WVFGRD96 19.0 60 60 10 4.80 0.5850
WVFGRD96 20.0 60 60 10 4.81 0.5796
WVFGRD96 21.0 60 60 10 4.82 0.5732
WVFGRD96 22.0 60 60 10 4.82 0.5669
WVFGRD96 23.0 60 60 10 4.83 0.5601
WVFGRD96 24.0 60 60 10 4.83 0.5529
WVFGRD96 25.0 60 60 10 4.84 0.5461
WVFGRD96 26.0 60 60 10 4.84 0.5394
WVFGRD96 27.0 60 60 10 4.85 0.5326
WVFGRD96 28.0 60 60 10 4.85 0.5254
WVFGRD96 29.0 60 60 10 4.86 0.5179
The best solution is
WVFGRD96 11.0 55 55 -15 4.76 0.6147
The mechanism correspond to the best fit is
|
|
Figure 1. Waveform inversion focal mechanism
|
The best fit as a function of depth is given in the following figure:
|
|
Figure 2. Depth sensitivity for waveform mechanism
|
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 component is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. A pair of numbers is given in black at the right of each predicted traces. The upper number 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 lower number gives the percentage of variance reduction to characterize the individual goodness of fit (100% indicates a perfect fit).
The bandpass filter used in the processing and for the display was
cut a -20 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
|
|
Figure 3. Waveform comparison for selected depth
|
|
|
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.
|
A check on the assumed source location is possible by looking at the time shifts between the observed and predicted traces. The time shifts for waveform matching arise for several reasons:
- The origin time and epicentral distance are incorrect
- The velocity model used for the inversion is incorrect
- The velocity model used to define the P-arrival time is not the
same as the velocity model used for the waveform inversion
(assuming that the initial trace alignment is based on the
P arrival time)
Assuming only a mislocation, the time shifts are fit to a functional form:
Time_shift = A + B cos Azimuth + C Sin Azimuth
The time shifts for this inversion lead to the next figure:
The derived shift in origin time and epicentral coordinates are given at the bottom of the figure.
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=Mon Apr 7 19:39:48 CDT 2014
Last Changed 2014/04/07
