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Identification of Cavities in Karst Areas Using Seismic Ambient Noise

Description: 

The identification and mapping of underground cavities is of significant importance in the context of urban development and civil engineering projects, as their undetected presence, whether of natural or artificial origin, poses a substantial geotechnical hazard. Also, the cavities produced by underground nuclear explosions (UNE) are of particular interest. The detection and location of a cavity generated by a UNE can serve as important evidence in the framework of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) on-site inspections. In order to enhance the capabilities of the CTBT on-site inspections, a Finite-Interval Spectral Power (FISP) methodology based on the ambient noise analysis has been developed for the detection of a deep underground cavity (Kristekova et al. 2021).

Applications of the FISP method included the two CTBTO field tests in the karst areas: a site near Felsőpetenyi in Hungary and the mountainous area in the vicinity of Rotmoos, Styria, Austria. In the first case in Hungary the seismic ambient noise was recorded on a grid of receivers (more favorable configuration) however in the case of the Austrian test data noise was recorded only on two separate receiver profiles, comprising 22 and 19 stations. This limited configuration was due to the difficult terrain in the mountains and hence also limited accessibility. However, the density of receivers along the profiles was higher than during the field test in Hungary. The objective of the Austrian test was to test on-site inspection methods in challenging terrain conditions and to identify cave targets of various sizes within a depth range of approximately 35 to 350 meters in a complex cave system. Six hours of relatively undisturbed noise data across the majority of the receivers were used for the calculation of the FISP values at several frequency bands. We have identified FISP anomalies that could be attributed to the presence of cavities and/or spatial variability of complex local geological conditions. These findings agreed well with the results obtained using electrical conductivity measurements and active seismic surveys.

Session: Geophysics in a Changing World: Monitoring Applications from Seismology and Beyond [Poster]

Type: Poster

Date: 4/15/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Miriam

Student Presenter: No

Invited Presentation: 

Poster Number: 49

Authors