Relative Time Corrections For Historical Analog Seismograms Using The Single-Day Ambient Noise Correlation Function

This study examines analog seismograms that were generated when most seismic stations had their own clock for timing, making precise comparison of time between different stations difficult. Availability of accurate relative timing facilitates differential travel-time analyses, such as seismic tomography and local earthquake relocations, to be performed using data originally recorded on paper or other physical media. These analyses allow for the investigation of longer-term processes like the earthquake cycle or climate change. We take advantage of the continuous nature of seismic noise to determine the relative time correction between two stations by leveraging the symmetry of the noise correlation function. This procedure is applied to two Global Positioning System-timed stations in the Hawaiian Volcano Observatory network demonstrating subsecond time accuracy. The technique is then applied to analog records from comparable stations between 7 and 10 August in 1988, and relative time corrections of up to about 6 s are obtained. These corrections are confirmed by the relative arrival times of teleseismic P waves of earthquake doublets.