This is a preliminary UCB moment tensor report for the swarm located
12 km N of Burney, CA on December 20, 2000. Moment tensor solutions for the
four largest events, Mw3.9, Mw3.7, Mw4.3 and Mw4.4 follow. All events have
northwest striking normal-type mechanisms and have a best fitting source
depth of 5km.
Best regards,
Douglas Dreger
UCB Seismological Laboratory
EVENT1 Date/Time:2000/12/20 14:55:51(PST) 40.986N 121.687W
Best Fitting Double-Couple:
Mo = 7.65E+21 Dyne-cm
Mw = 3.89
Z = 5 km
Plane Strike Rake Dip
NP1 175 -57 52
NP2 308 -125 49
Principal Axes:
Axis Value Plunge Azimuth
T 7.650 2 242
N 0.000 26 333
P -7.650 64 149
Moment Tensor: Scale = 10**21 Dyne-cm
Component Value
Mxx 0.640
Mxy 3.812
Mxz 2.460
Myy 5.565
Myz -1.732
Mzz -6.206
EVENT2 Date/Time: 2000/12/20 14:59:38(PST) 40.988N 121.689W
Best Fitting Double-Couple:
Mo = 4.35E+21 Dyne-cm
Mw = 3.73
Z = 5 km
Plane Strike Rake Dip
NP1 185 -61 55
NP2 321 -125 44
Principal Axes:
Axis Value Plunge Azimuth
T 4.350 6 255
N 0.000 23 348
P -4.350 66 151
Moment Tensor: Scale = 10**21 Dyne-cm
Component Value
Mxx -0.285
Mxy 1.381
Mxz 1.317
Myy 3.846
Myz -1.226
Mzz -3.561
EVENT3 Date/Time: 2000/12/20 15:22:54(PST) 40.990N 121.698W
Best Fitting Double-Couple:
Mo = 3.72E+22 Dyne-cm
Mw = 4.35
Z = 5 km
Plane Strike Rake Dip
NP1 178 -65 57
NP2 318 -123 40
Principal Axes:
Axis Value Plunge Azimuth
T 3.722 9 251
N 0.000 20 344
P -3.722 67 138
Moment Tensor: Scale = 10**22 Dyne-cm
Component Value
Mxx 0.081
Mxy 1.392
Mxz 0.791
Myy 2.994
Myz -1.442
Mzz -3.074
Event Date/Time: 2000/12/20 15:39:14(PST) 40.989N 121.697W
Best Fitting Double-Couple:
Mo = 4.26E+22 Dyne-cm
Mw = 4.39
Z = 5 km
Plane Strike Rake Dip
NP1 164 -70 54
NP2 312 -115 41
Moment Tensor: Scale = 10**22 Dyne-cm
Component Value
Mxx 0.937
Mxy 2.025
Mxz 0.510
Myy 2.886
Myz -1.369
Mzz -3.823
Principal Axes:
Axis Value Plunge Azimuth
T 4.260 7 240
N 0.000 16 331
P -4.260 73 128
Focal Mechanism for EVENT4
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