Application Examples and Capabilities of Combining Passive Seismic Methods to Study Depth Structure of the Earth’s Crust

Abstract—The capabilities of a combination of passive seismic methods to study the geological structure of the upper part of the Earth’s crust compared to active methods are analyzed using case examples. The passive methods include microseismic sounding, Nakamura’s horizontal-to-vertical spectral ratio method (HVSR), seismic interferometry, and, for anthropogenic sites, ambient vibration testing using industrial signals. Three examples are considered: a zone of a platform tectonic earthquake, a kimberlite pipe, and a hydroelectric dam with foundation site. The results of the passive and active seismic methods agree well. Passive methods give more diffuse horizontal boundaries but clearly identify near-vertical heterogeneities. Combining passive methods is effective for reconnaissance studies and in the remote regions that are difficult to access by active observation techniques. Combination of passive methods enables simultaneous processing of seismic records obtained through different passive methods, with a minimum of two sensors required.