The seismic data archived in this database came from several European Institutions^(a), using many kinds of instrumentation. The oldest part of the original data (years < 1990 about) was in analogical form: magnetic tape F.M. recordings, using a more or less 'Mars-66'^(b) scheme.
         
A first dedicated systems were implemented in our Laboratory, using both Harware and Software dedicated tools, in order to get the proper A/D conversion procedure^(c). The 1995 'new' implemented system^(d) was the following:

Simplified scheme of the system implemented for the analog signal processing and digital conversion:             - controlled play-back (with monitor and paper copy) - PLL system (using demodulator pilot frequency) which controls the A/D clock - buffered syncronization and transfer data-blocks - external final transfer to the PC and Ethernet (Internet) for further digital processing.

         
In general for each useful seismic recording ('waveform') the needed information were^(e):
 

Shot point data:
Shot-point Id.			Date	Shot Time	geographycal Coordinates	charge [kg]	Altit. [m]	[Bathym.] [m]	[charge depth] [m]
O			E	E	E	O	O	O	O
Recording point (temporary seismic 'station') data:
Shot-point Id.	Profile Id.	Rec. point Id.	Date	Time signal	geographycal Coordinates	Sensor(s)	Data logger	Operator	Institute (Country)
O	E	E	O	E	E	O	O	O	O

               
The special software implemented for the proper A/D conversion needs of ALL the E parameters. In fact only a correct knowledge of space and time coordinates of both the seismic source and recording point, could produce a useful digital seismic record, defined as a file composed by an 'header' record (see format) followed by the numerical sequence of amplitude values, sampled at a constant dt (with respect to the recorded time signal). This file is what we call a 'waveform'.
           
Many of the original analog tapes and/or cassettes are still available at our Unit of Milan (see analog-tapes collection).
Some of them (as explained in our 'missing data' page) came without the necessary information; so it was usefulness to digitize them.
We apologize for the lack of these seismic data in our archive (less than 10% of the available dataset, mainly the oldest recordings, in any case well known to the INGV-MI 'DOL' Committee).
               

---

a)  see 'credits' page
b)  Berckhemer H. (1970). MARS-66: a magnetic tape recording equipment for Deep Seismic Soundings. Zeitschrift für Geophysik, 36, 501-518.
c)  Maistrello M. (1985). Acquisizione ed elaborazione digitale dei dati sismici a rifrazione profonda (D.S.S.) per lo studio di strutture crostali. Milan State University, Degree Thesis, 150 pp + ann. sw printouts.
d)  Maistrello M. (1996). MENU_HP: una procedura unificata per la digitalizzazione, elaborazione, archiviazione, trasmissione di segnali sismici analogici in ambiente Basic-HP. CNR-IRRS int. Report; 2/'96; 68 pp
e)  E=Essential; O=Optional