Solution details

This is a deviatoric moment tensor solution and would not properly represent an explosive earthquake source. The moment tensor is a simplified representation of the seismic source that assumes that the earthquake occurred on one point on the map. Slip on a planar fault results in a pure double couple source. The moment tensor allows for sources that are more complicated than that. Any non-double couple components should be regarded with suspicion as they can be caused by a flawed velocity model (and corresponding synthetic seismograms). Currently, we use simple 1D velocity models that work well to locate earthquakes, however, we have not yet adequately tested how well they reproduce long-period ground motions. The double couple fault plane solution tends to be fairly robust and often compares well with the P wave first motion focal mechanism. The depth of this event is not well-constrained by the moment tensor inversion. For a depth of 52 km we got a slightly higher variance reduction, however, we prefer the 55km solution since it has a smaller non-double couple component (3% vs. 10% with 52 km depth).

Solution parameters for 09013013245p Number of stations 23 Period range of data 20-50s Data type full waveform velocity traces Preferred event depth 55 km (not well-constrained) Scalar Moment 6.90939 dyn-cm Moment Magnitude 4.5 Variance Reduction 74.28 % Percent Double Couple 97.0 % Percent CLVD 3.0 % Solution Quality EXCELLENT

Waveform Matches

Instrument-corrected and bandpassed (20-50s) velocity traces are shown in black. Synthetics are shown in red and also have been bandpassed (20-50s). The velocity model used was vel.P3: P Velocity (km/s) Top of Layer (km) 5.40 0.0 6.38 4.0 6.59 9.0 6.73 16.0 6.86 20.0 6.95 25.0 7.80 41.0 Shear wave velocities are calculated from the Pwave velocities using a Vp/Vs ratio of 1.78.