Development of tomography method for the critical point of stress-strain state

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Ocean tides are a well-known phenomena resulting from periodic variations in the gravitational attraction of the Sun and the Moon. The Earth's response to ocean tidal loads (OTL) is controlled by internal variations of density and elastic parameters. In principle, observations of the Earth's OTL response can be used to constrain our models of Earth's internal structure.The OTL response has a richer spatial structure including power at regional length scales (a few hundred kilometers) with typical amplitudes on the centimeter scale. We present the first depth-dependent model for the crust and upper-most mantle that constrains independently density and elastic moduli below the western United States and nearby off shore regions. We find that at least regionally, there is a low-density anomaly in the asthenosphere of about 50 kg/m3, corresponding to a temperature anomaly of about 300℃. Such a temperature anomaly can also explain differences in inferred elastic structure relative to globally averaged radial seismic models.