Prediction of ground motion spectra on solidly frozen bedrock during large earthquakes

Two methods are discussed for determining changes in ground displacement spectra and the velocity and acceleration spectra derived from these when recorded on solidly frozen bedrock (T < −3°C) versus epicentral distance and energy class. The first of these methods characterizes the entire epicenter field of earthquakes, while the second aims at studying possible differences between spectra in different source zones. We have found the maximum spectral level as a function of epicentral distance and energy class. The calculated spectra are compared with the available records of large earthquakes. The manner in which near and comparatively small earthquakes can be used to find ground motion spectra is shown for solidly frozen bedrock for earthquakes as large as the 15–17 energy class, as well, determination of the differences between the spectra of seismic signals due to earthquakes occurring in different source zones is performed. The results can be used both directly and for the zonation and prediction of seismic hazard within the zone of solidly frozen rock, and also for the case where the temperature regime of the frozen rock has been changed or disturbed.