Fig. 8. Signal spectrum of the Martian stress field: (a) the degree variances, and (b) the cumulative degree variances of the stress intensity (in MPa2).Figure optionsDownload full-size imageDownload high-quality image (202 K)Download as PowerPoint slide
Most of the horizontal stress intensity AG-337 generated by crustal structures which are not fully isostatically compensated. This is evident, for instance, in the presence of the stress anomalies around volcanoes of Olympus and Elysium Mons and Tharsis Montes. These stress anomalies are propagated to the higher-frequency spectrum (above degree 70). The stress field of the isostatically uncompensated crustal structures underlying impact craters, on the other hand, occupies mainly the medium wavelengths. The stress field along Valles Marineris has a broader spectral signature. The long-wavelength stress field is investigated in the next paragraph.
4.2.6. Long-wavelength stress field
The long-wavelength part of the Martian sub-crustal stress field, which includes spherical harmonics up to degree 5, is shown in Fig. 9. Most of the stress anomalies are distributed in the Tharsis region, showing some circular symmetry with the minimum intensity in its center and an increasing intensity towards Tharsis margins. This circular pattern of the stress anomalies is very similar to that we observe around major volcanoes. This stress field is thus likely caused by a crustal load of the Tharsis bulge. Moreover, the orientation of stress vectors is systematically convergent in the prime-vertical direction, while divergent in the meridional direction. The crustal load is – in this case – manifested by the prime-vertical compressional stress coupled by the meridional tensional stress.
Most of the horizontal stress intensity AG-337 generated by crustal structures which are not fully isostatically compensated. This is evident, for instance, in the presence of the stress anomalies around volcanoes of Olympus and Elysium Mons and Tharsis Montes. These stress anomalies are propagated to the higher-frequency spectrum (above degree 70). The stress field of the isostatically uncompensated crustal structures underlying impact craters, on the other hand, occupies mainly the medium wavelengths. The stress field along Valles Marineris has a broader spectral signature. The long-wavelength stress field is investigated in the next paragraph.
4.2.6. Long-wavelength stress field
The long-wavelength part of the Martian sub-crustal stress field, which includes spherical harmonics up to degree 5, is shown in Fig. 9. Most of the stress anomalies are distributed in the Tharsis region, showing some circular symmetry with the minimum intensity in its center and an increasing intensity towards Tharsis margins. This circular pattern of the stress anomalies is very similar to that we observe around major volcanoes. This stress field is thus likely caused by a crustal load of the Tharsis bulge. Moreover, the orientation of stress vectors is systematically convergent in the prime-vertical direction, while divergent in the meridional direction. The crustal load is – in this case – manifested by the prime-vertical compressional stress coupled by the meridional tensional stress.