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Analysis of recent lunar seismic data from distant meteoroid impacts, high‐frequency teleseismic events and deep moonquakes shows several significant deviations of P‐ and S‐wave travel times from those expected if the lunar interior were homogeneous below the crust. These data are interpreted resulting in a lunar model consisting of at least four and possibly five distinguishable zones: (I) the 50 to 60 km thick crust characterized by seismic velocities appropriate for plagioclase‐rich materials, (II) the 250 km thick upper mantle characterized by seismic velocities consistent with an olivine‐pyroxene composition, (III) the 500 km thick middle mantle characterized by a high (0.33 ‐ 0.36) Poisson's ratio, (IV) the lower mantle characterized by high shear‐wave attenuation and possibly (V) a core of radius between 170 and 360 km characterized by a greatly reduced compressional wave velocity.
Nakamura et al. (Mon,) studied this question.