Complex sentence: Since 2001 the VAN team has tried to improve the accuracy of the estimation of the time of the forthcoming earthquake by introducing the concept of "natural time", a parameter which puts weight on a process based on the ordering of events.
Split into simpler sentences: Since 2001 the VAN team has tried to improve the accuracy of the estimation of the time of the forthcoming earthquake. Their methodology involves the introduction of the concept of "natural time", a parameter which puts weight on a process based on the ordering of events.