Complex sentence: Most anisotropy parameter estimation work is based on shale and silts, which may be due to the fact that shale and silts are the most abundant sedimentary rocks in the earth's crust.
Split into simpler sentences: Most anisotropy parameter estimation work is based on shale and silts. It may mainly due to the fact that shale and silts are the most abundant sedimentary rocks in the earth's crust.