Visual inspection for CTBT verification

On-site visual inspection will play an essential role in future Comprehensive Test Ban Treaty (CTBT) verification. Although seismic and remote sensing techniques are the best understood and most developed methods for detection of evasive testing of nuclear weapons, visual inspection can greatly augment the certainty and detail of understanding provided by these more traditional methods. Not only can visual inspection offer ``ground truth`` in cases of suspected nuclear testing, but it also can provide accurate source location and testing media properties necessary for detailed analysis of seismic records. For testing in violation of the CTBT, an offending party may attempt to conceal the test, which most likely will be achieved by underground burial. While such concealment may not prevent seismic detection, evidence of test deployment, location, and yield can be disguised. In this light, if a suspicious event is detected by seismic or other remote methods, visual inspection of the event area is necessary to document any evidence that might support a claim of nuclear testing and provide data needed to further interpret seismic records and guide further investigations. However, the methods for visual inspection are not widely known nor appreciated, and experience is presently limited. Visual inspection can be achieved by simple, non-intrusive means, primarily geological in nature, and it is the purpose of this report to describe the considerations, procedures, and equipment required to field such an inspection