Particle filter code with an example of subsidence caused by a compacting reservoir

A compacting reservoir gives a subsidence field at the Earth's surface. The subsidence field has a varying smoothness given the reservoir compaction field, with, for example a very smooth subsidence bowl or a very spatially uncorrelated subsidence field.In this code, we implement a particle filter in a static case to estimate model states and illustrate its implementation with two subsidence models providing varying smoothness of the subsidence field.