Digitizing analog seismograms of Iranian seismic stations — preserving records for strong earthquakes in Iran 1960–1990

Abstract

To preserve the analog records of historical earthquakes which occurred in and around Iran in digital form and to make them available for modern analysis techniques that require waveforms, we decided to digitize seismograms of destructive earthquakes that occurred between 1960 and 1990. The seismograms have been recorded at five seismic stations deployed in Tehran, Mashhad, Kermanshah, Tabriz, and Shiraz by the Institute of Geophysics of the University of Tehran (IGUT). The restoration project of the old analog seismograms archived in the IGUT started in 2018. Seismograms were sorted by station and date to create a hardcopy databank, and then those from large earthquakes and their larger aftershocks were chosen for the scanning process. Seismograms of 52 significant earthquakes and their aftershocks with magnitudes greater than 5.0 that occurred in and around Iran were scanned. Besides that, seismograms of several significant and huge teleseismic earthquakes that occurred between 1960 and 1990 were scanned. At present, almost 600 scanned seismograms are available. The current digitization process in IGUT is done manually and is based on waveform vectorization. The provided databank is one of the most important sources of information for research in seismology and active tectonics in and around Iran.