However the overall seismic risk at the INEEL is low. The Snake River Plain itself is generally aseismic. While earthquakes occur in the Basin and Range Province, they generally do not on the basaltic Plain. One hypothesis for this is that the extensional strain on the Plain is taken up by dike injection rather than normal faulting. In general the basalts are poor transmitters of seismic energy, acting as a sponge to ground motion.

Earthquakes are an obvious hazard in active parts of the Intermountain Seismic belt. The most active normal faults of the Basin and Range province near the INEEL are the central parts of range-front faults, rather than their southern ends. This is due to the migration of seismic acfivity away from the Snake River Plain with time.

The southern ends of the Lost River, Lemhi, and Beaverhead faults are adjacent to the INEEL, and thus of considerable interest. The Arco fault segment of Lost River Fault has average slip rate of 0.1 to 0.12 m per 1000 years in past 160,000 years. This fault has not ruptured in the past 30,000 years. Fault is either overdue (by 10,000 to 20,000 years), or perhaps dying. The southern segments of the Lemhi fault (Howe segment) and Beaverhead fault have been similarly quiet in the last 30,000 years.

The Borah Peak earthquake produced peak ground accelerations in the vicinity of the INEEL of 0.022 to 0.078 g, with a Modified Mercalli Intensity of VI. A predicted peak ground acceleration from a 7.25 magnitude earthquake on the Arco or Howe segments would produce a peak horizontal ground acceleration of 0.22 g. It is to this standard that INEEL facilities are designed.

The locus of rhyolitic caldera-forming eruptions has moved to Yellowstone, and the risk of these at the INEEL is minimal. In addition, prevailing winds generally are eastward, so the risk of even a major ash fall is thought to be low.

Intrusion of rhyolite domes on the Snake River Plain has occurred in the last 500,000 years, and could occur again. The domes seem to be concentrated on the northeast-trending axial volcanic zone, and no INEEL facilities are built on that zone. These allegedly would be a hazard only within 10 km of the intrusion.

Inundation from basaltic lava flows is a significant hazard on the INEEL. The last volcanic activity on the Great Rift area was 2,100 years ago; the Hells Half-acre flow is dated at 5200 years ago; and the North and South Robers and Cerro Grande fields are dated at 12,000 to 13,400 years ago.

There is not thought to be significant danger from earthquakes related to basaltic eruptions. Likewise, inflation or deflation of the ground surface are not thought to represent significant risks. Impacts from volcanic gases are even lower. The hazard due to seismicity associated with dike intrusion and volcanism is less than the hazard due to seismicity due to tectonic processes

One of the associated geologic hazards with rapid uplift and normal faulting is landslides or, more generally, mass wasting, produced by gravitational instability combined with saturation of the soil, removing support from the toe of a slope, loading the upper slope, or structural weaknesses in the rocks. Large landslide masses are found in several of the Neogene valleys of southeast Idaho, especially the Palisades Reservoir area, and possibly the Pocatello valley.

Especially prone to mass wasting are the unconsolidated sediments deposited in Lake Bonneville, now found in Cache Valley and Malad Valley.

The Bear River Landslide complex north of Preston represents adjustment of the lake silts to the erosion produced by the drop in base level as Lake Bonneville fell from the Provo level to its present shoreline elevation.