Table 3. Criteria Used to Remove Poorly Constrained Events

Criterium number

Criterium

Value

1

Condition number

< 100

2

Weighted RMS residual

< 2.0 s

3

Closest station distance

< 150 km

4

Azimuth gap

< 200 degrees

5

Average residual

< 1.0 s

6

Theoretical location error

< 10 km

7

Final iteration step

< 3 km

8

Depth

> 0.1 km

9

Horizontal shift

< 10 km

10

Vertical shift

< 10 km

The criteria were applied after relocation. Criteria 1, 3, and 4 check that a good station geometry is used to determine the location. Criteria 2 and 5 check that the location provides a reasonable fit to the data. Criterion 7 checks that the solution converges. Criterion 8 was required to remove a significant number of events that attempted to converge to a location above ground. Criteria 9 and 10 were used during the 1-D and 3-D inversion iterations to remove any events that were shifted a significant amount when relocated in the new velocity models.