Roger:

OK... But...

See depths:

REF: { Double Fatal (Rockburst) Fall of Ground Accident, June 5, 2001 Galena Mine,
Coeur Silver Valley Inc.
Wallace, Shoshone County, Idaho }

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search parameters are:

catalog=CNSS
start_time=2001/04/15,00:00:00
end_time=2001/07/20,23:59:59
minimum_latitude=47.0
maximum_latitude=47.9
minimum_longitude=-116.4
maximum_longitude=-115.4
minimum_magnitude=0.0
maximum_magnitude=9.0
event_type=A
include events with no magnitude
Date Time Lat Lon Depth Mag Magt Nst Gap Clo RMS SRC Event ID
----------------------------------------------------------------------------------------------
2001/04/19 20:41:40.80 47.4640 -115.8010 0.60 1.60 Mc 9 195 59 0.27 MB
2001/04/25 21:04:07.40 47.4720 -115.7840 0.20 2.00 Mc 14 186 58 0.16 MB
2001/05/05 01:27:25.60 47.4630 -115.7700 6.10 1.60 Mc 11 186 57 0.10 MB
2001/05/08 06:36:36.80 47.4730 -115.7820 0.30 3.00 l 28 0.00 BUT 200105084011
2001/05/08 07:38:38.00 47.4890 -115.7830 0.80 1.40 Mc 9 193 57 0.19 MB
2001/05/09 06:35:36.50 47.4600 -115.8080 0.80 1.60 Mc 12 187 60 0.15 MB
2001/05/28 13:48:22.80 47.4770 -115.9740 2.50 1.70 Mc 11 191 72 0.24 MB
2001/06/03 07:55:45.20 47.4890 -115.9830 5.90 1.70 Mc 11 191 72 0.25 MB
2001/06/05 19:41:51.40 47.4900 -115.9690 2.00 2.00 Mc 15 189 71 0.34 MB
2001/06/05 22:52:03.50 47.4810 -115.8000 1.90 1.80 Mc 12 184 59 0.24 MB
2001/06/12 20:36:45.10 47.4790 -115.7890 2.00 1.70 Mc 12 185 58 0.28 MB
2001/06/20 04:13:35.60 47.4970 -115.9890 7.80 1.40 Mc 6 210 72 0.08 MB
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The 6-5-02 "rockburst" event occuring at 19:41:51 but the "eq."/"rockburst" depth does not coincide with the two depths of the mining operation (4300 & 4600 foot levels). The fatalities were at the 4600 (foot?) level.

What this means is one of the following:
1) Somebody botched the depth calculation and the actual depth was 4600 feet (as you say)
2) The depth calculation was correct (either 2 miles or 2 kms ) and the 4600 feet level = 1.56 ? kms (close). Maybe there's an error associated with depth that allows it to be at the 4600 level.
3) ==>The "rockburst" label is an expression of earthquake phenomena which is expressed in or near mining operations and is thought (mistakenly?) to be associated with improper support of the tunnel itself. (BTW, how much support do you need to keep the tunnel from caving from an equivalent Mag. 5 eq. "rockburst") ?

In the CNSS listing also note the eqs at depths of 6.10, 5.90, and 7.8 (kms or miles?) within the same general area. These are happening below the 4600 foot tunnel area. By your definition (and mine) these must be earthquakes. I suggest that the "rockburst" event is also an earthquake process ...and that it would be difficult if not impossible to "secure" any mine from possible future damage from so called "rockbursts".

As usual, I'm just adding my $.02 worth.

• Fatal Rockburst in Idaha Silver Mines