There actually has been some research into the question of triggering seismic activity through engineered processes. If human activity cannot trigger a volcano directly, it can trigger earthquakes. A large earthquake, then, might trigger volcanic activity.
A 2003 academic paper by three Chinese scientists discusses small events triggering large earthquakes. Also, testimony from 1971, given before the United States Supreme Court, discussed the seismic effects of a large thermonuclear detonation.
Considering the size of the Yellowstone Caldera -- a 45-mile by 30-mile, 8,000 foot crater -- and the presence of large fault lines and caves which extend into the Caldera, the following far-out possibility may exist: two extremely large detonations (multi-megaton range?) in the two large fault lines bisecting the Caldera from the south could maybe generate forces sufficient to incise the magma chamber and thus trigger a deep volcanic eruption from Yellowstone.
This scenario really seems about the most remote, misguided and ridiculous possibility -- that even the most clever and well-equipped enemy could never even hope to prepare. However, multiple posts on this thread have expressed some concern over caves, fault lines, and the Yellowstone Super-volcano.
Here are a couple of sources for this balderdash.
I.
http://www.iop.org/EJ/abstract/0256-307X/20/9/312 Small Stress Change Triggering a Big Earthquake: a Test of the Critical Point Hypothesis for Earthquakes
Wan Yong-Ge1, Wu Zhong-Liang1,2,3 and Zhou Gong-Wei1
1 China Seismological Bureau, Beijing 100081
2 Graduate School, Chinese Academy of Sciences, Beijing 100039
3 The Abdus Salam International Center for Theoretical Physics, Trieste 34100, Italy
Received 14 April 2003
Abstract. Whether or not a small stress change can trigger a big earthquake is one of the most important problems related to the critical point hypothesis for earthquakes. We investigate global earthquakes with different focal mechanisms which have different levels of ambient shear stress. This ambient stress level is the stress level required by the earthquakes for their occurrence. Earthquake pairs are studied to see whether the occurrence of the preceding event encourages the occurrence of the succeeding one in terms of the Coulomb stress triggering. It is observed that the stress triggering effect produced by the change of Coulomb failure stress in the same order of magnitudes, about 10-2MPa, is distinctly different for different focal mechanisms, and thus for different ambient stress levels. For non-strike-slip earthquakes with a relatively low ambient stress level, the triggering effect is more evident, while for strike-slip earthquakes with a relatively high ambient stress level, there is no evident triggering effect. This water level test provides an observational support to the critical point hypothesis for earthquakes.
II.
http://www.elr.info/litigation/vol1/1.20534.htm The Committee for Nuclear Responsibility, Inc. v. Schlesinger
No. A-483 (U.S. November 6, 1971)
[Excerpted]
That more should be required is clear from the heretofore secret memorandum written by Russell Train of the CEQ, the agency charged with the broadest statutory authority in establishing national environmental policy.
According to Mr. Train,
"All the earthquakes triggered by underground explosions in the various Nevada tests released substantially less energy than the explosion itself. If one could establish that this is a necessary condition then there would be no apprehension with regard to the CANNIKIN event. Unfortunately, this is not the case. The magnitude of the triggered earthquakes will depend on the state of strain in the crust in the general region at which the underground explosion is set off. Extrapolation from the Nevada experience is uncertain because of the fundamentally different geologic setting between Nevada and the Aleutians. Further, experience with MILROW [a one megaton underground detonation set off on Amchitka in 1969] does not provide a sure basis for extrapolation. In the highly nonlinear phenomena involved in earthquake generation, there may be a threshhold value of the strain that must be exceeded prior to initiation of a large earthquake." Train memo, p. 4.
Mr. Train goes on to explain that "great earthquakes" [those with a force of 8.0 or more on the Richter scale] are now considered to result from the cumulative effects of a series of smaller shocks. (CANNIKIN is expected to register about 7.0 on the Richter scale). Referring specifically to great earthquakes occurring within the past few years in Chile and Alaska, he notes that the theoretical explanation for these events justifies a concern that the force of CANNIKIN, which would be the largest underground device exploded by man, might surpass the "threshhold" required to trigger a great quake.
"The suggested explanation of the Chilean and Alaskan earthquakes in terms of a succession of smaller earthquakes would support this interpretation. In this model a number of lock points stabilize a fault. Once one lock point is broken, sufficient energy may be released to break other lock points. If the stored strain energy is large, then the triggered earthquake could be of much greater magnitude than the triggering event. The underground explosion could serve as the first domino of the row of dominoes leading to a major earthquake.The major fault in the general region of Amchitka is thought to be some 40 km. beneath the test shot. The strain field will certainly be altered at this depth by the underground explosion. Observations of the BENHAM event [a one megaton detonation at the Nevada test sites] showed strains exceeding tidal strains at 29 km." Train memo, p. 4.
The CANNIKIN yield may be as high as five times that of the BENHAM and MILROW devices.
The "lock-point" theory is also explained in a statement by J. W. Hadley, which had also been suppressed until this week. The theory is nowhere discussed, nor even "alluded to," in the Impact Statement.
A further misleading conclusion in the Impact Statement is that CANNIKIN could not trigger a natural quake unless that quake "is imminent, very near the test site." The documents revealed this week indicate there is a possibility that earthquakes may be triggered by a rise in underground fluid levels, or by artificial loading of the earth's crust. Presumably, the fluid lubricates the rock along a fault line, thus enhancing the potential for slippage. A series of earthquakes along a dorment fault near Denver has been definitely attributed to the pumping of waste water deep into the earth by the Rocky Mountain Arsenal. Train memo, p. 1-2.
"A second example is found in the case of earthquakes associated with large lakes or reservoirs. As a result of loading of the earth's crust by these large bodies of water or by the modification of the groundwater flow or for some other reason not yet understood, substantial earthquakes have been associated with construction of large artificial lakes. A resent earthquake near Koyna Dam in India located in an area that is not normally seismic killed about 200 people. Similarly, many small earthquakes occurred when Lake Mead was filled." Train memo, p. 3.
Increased subsurface fluid pressure will be one result of CANNIKIN.
"the explosion will alter the pressure regime in the groundwater. The water pressure in the rocks interstices will increase due to the compaction of the ground around the cavity. . . . This increase in the fluid pressure will reduce the friction between fracture separated blocks. The effect would be greatest on faults oriented parallel to the residual compressive stresses resulting from the test explosion. Thus, it is possible that the mechanism involved in the Denver earthquake would raise the probability of triggering a large earthquake." Train memo, p. 3.
Thus, it would appeal that "imminence" may not be necessary for CANNIKIN to trigger a large earthquake. This possibility is not mentioned in the Impact Statement.
Another failure of the Impact Statement is to consider the long-term effects of the CANNIKIN device on the geology. "The creation of a large cavity together with a later collapse of the chimney produces permanent changes in the strain field. . . . However, the strain field resulting from an underground explosion cannot be calculated with any precision because of the dependence of the field on the detailed geology which is largely unknown at any given location." Train memo, p. 3.
Not only does the Impact Statement fail to assess the possible effects of permanent changes in the strain field, but it represents that the geologic conditions at Amchitka have been fully explored.I.S., p. 19.
Perhaps the most striking deception of the Impact Statement, in light of the Train memo, is its attempt to represent that professional opinion is unanimous that there is no real danger that CANNIKIN will trigger a large earthquake. According to Mr. Hadley, however,
"Qualified scientific opinion is in good agreement that the possibility of triggering a large earthquake by CANNIKIN is remote, but real. . . . Variation of technical opinion from this position is minor." Hadley memo, p. 6.