The Dixie Valley earthquake sequence actually began on July 6, 1954 with a Ms 6.8.
This was followed by an extensive aftershock sequence including events on July 6 - Ms 6.4;
August 23 Ms 6.8; and Dec 16 Ms 7.3. The catalog of know nuclear explosions does
not show any tests conducted during this time frame (see link below). An unusual
seismic disturbance of Ms 5.5 did occur on July 2, 1954 at 38.1N 116.3W, north of the
Nevada test site (NTS). This might have been an unannounced test, as it is not listed
as an earthquake in the 1954 U.S. Earthquakes publication, but was recorded
by ISS, BRK, REN, ROT, MRO as a sizable disturbance. That U.S. earthquakes
did not record this event may mean they had information which is no longer available
regarding a test at that time.

On the other hand, it seems more likely to me that this the beginning of this sequence
on July 6 was a far-field aftershock from an earthquake of Ms 7.1 which occurred
three hours before in the Northern Kuril Islands. I will explain:

The earthquake in the northern Kuril Islands occurred with the following parameters:

O: 06JUL2001 08:04:37 46.5N 153.4E Ms=7.1 SSR Northern Kuril Islands

There was a foreshock to the Ms 6.8 Dixie Valley earthquake which had the
following parameters:

O: 06JUL2001 10:09:36 39.5N 118.8W Ml=3.0 BRK Dixie Valley, NV

The LQ surface wave moves at 2.4 degrees/minute. The distance from Dixie
Valley to the Kuril mainshock was 61 degrees (a distance at which FFA triggering
is expected). For a wave going around the long way, the distance is 299 (360-61) degrees.
The time for such a wave to arrive at Dixie Valley from the Kurils is 299/2.4= 125 minutes.
Note that the time between the Kuril event and the subsequent Dixie Valley foreshock
is also 125 minutes 08:04:37 to 10:09:36. This suggests that the foreshock was
triggered by the passage of the LQ wave from the Kuril Islands.
The Dixie Valley mainshock likewise occurred within a few minutes after the passage
of the Rayleigh wave from the Kurils, again suggestive of a triggering as a FFA from
the Kurils.
This whole sequence takes a bit of explanation, so please bear with me.
A surface wave can take a number of paths from epicenter to a subsequent location.
The first is the most direct (the shortest distance between the two points on a sphere) -
in this case this is 61 degrees. The second will go around the earth the opposite
way and will travel a distance of 360 minus 61 degrees = 299 degrees.
For large earthquakes waves can continue traveling for several days and may make
many trips around the earth. So we can consider other waves as well which travel
the following distances from the Kuril Islands to Dixie Valley, NV:

1) 61 degrees
2) 360 - 61 = 299 degrees
3) 360 + 61 = 421 degrees (one trip around plus distance)
4) 720 - 61 = 659 degrees
5) 720 + 61 = 781 degrees (two trips around plus distance)
6) 1080 - 61 = 1019 degrees
7) 1080 + 61 = 1141 degrees

etc.

Now we can consider the times it takes to travel these distances. There are two
surface waves, the Love (Lq) wave which travels at approximately 2.37 degrees per minute and
the Rayleigh (Lr) wave which travels at about 2.24 degrees per minute over this path.

From this we can determine when these waves will be at Dixie Valley:

Distance 1: 61 degrees
LQ: 61/2.44 = 25 minutes
LR: 61/2.24 = 27 minutes

Distance 2: 299 degrees
LQ: 299/2.44 = 123 minutes = 2 hours 3 minutes Foreshock Ml 3.0: 2 hours 5 min.
LR: 299/2.24 = 137 minutes = 2 hours 17 minutes

Distance 3: 421 degrees
LQ: 421/2.44 = 172 minutes = 2 hours 52 minutes
LR: 421/2.24 = 187 minutes = 3 hours 7 minutes Mainshock Ms 6.8: 3 hours 9 min.

Distance 4: 659 degrees
LQ: 659/2.44 = 269 minutes = 4 hours 29 minutes
LR: 659/2.24 = 294 minutes = 4 hours 53 minutes Aftershock Ml 4.9: 4 hr. 53 min.

Distance 5: 781 degrees
LQ: 781/2.44 = 319 minutes = 5 hours 19 minutes Aftershock Ml 4.5: 5 hr. 30 min.
LR: 781/2.24 = 347 minutes = 5 hours 47 minutes

Distance 6: 1019 degrees
LQ: 1019/2.44 = 417 minutes = 6 hours 57 minutes Aftershock Ml 4.5 : 6 hr. 53 min.
LR: 1019/2.24 = 453 minutes = 7 hours 36 minutes Aftershock Ml 4.4 : 7 hr. 47 min.

Distance 7: 1141 degrees:
LQ: 1141/2.44 = 467 minutes = 7 hours 47 minutes Aftershock Ml 4.4: 7 hours 47 min.
LR: 1141/2.24 = 507 minutes = 8 hours 27 minutes Aftershock Ml 3.7 : 8 hours 26 min.

So, of the 12 events recorded at Dixie Valley between 08:00 and 17:00 on July 6, 1954, 6
(half) match the arrival times of LQ or LR waves from the Kurils within a few minutes. It
would appear that FFA triggering was quite prominent in this and the effects of nukes
are likely to be discounted.

, This is just an example of how such as question as raised by Petra can be answered
and how sometimes we can figure things out for ourselves without appealing
to a higher authority (although that never really hurts anything).

• Catalog of Nuclear Explosions