ULTRA BROAD-BAND SEISMOLOGY ON INTERMARSNET

Very broad band seismometers, which are included in the baseline of th e InterMarsNet payload cover the whole frequency band from tidal frequ encies up to 50 Hz. By using the results of field tests performed on E arth with the deployment scenario of the InterMarsNet seismic experime nt, it is shown that it should probably be possible to reach very low micro-seismic noise level, possibly less than a spectral amplitude of 10(-9) ms(-2) Hz(-1/2) on the vertical component. Despite the fact tha t only three stations will be available for the network, sufficient in formation should be available in the three-component short period reco rds to determine the location of Marsquake foci and the origin time to a level that will enable studies of the seismicity, interior velocity structure, and tectonic activity of the planet. Despite the fact that the most current signals will be recorded in the frequency band 10 mH z-10 Hz, it is shown that the detection of a quake of moment 10(18) N m, or the stack of the InterMarsNet records of quakes with a moment gr eater than 10(17) N m will allow normal mode frequency measurement in the range 5-20 mHz for a noise amplitude of 10(-9) m s(-2) Hz(-1/2) Ob servation in the range 3-5 mHz cannot also be ruled out. These normal mode frequencies will have a high scientific return for determining th e deep Mars structure. At longer periods, the detection of the tides o f Phobos will provide information on the deep internal structure even if no strong quakes are recorded. It is shown that the amplitude of th e Phobos tide fundamental after the analysis of a 2 year time series f rom a single station, for a realistic and conservative estimate of the long period noise may be measured with a precision of 1%. For less no ise scenario, and/or by using the stack of all the records, informatio n from the higher Phobos tidal harmonics will also be obtained. Copyri ght (C) 1996 Published by Elsevier Science Ltd