The New Madrid fault is totally different from the faults in California. The earth in and around the New Madrid fault lines are covered with millions of years of river silt, clay, and other soft strata. It is several miles underground making observation of its activity difficult at best. The most observable activity is the sand boils. They usually indicate pressure pushing up to the surface. The faults in California are within harder, drier strata, making them much easier to see, even with the naked eye. The plates which make up the faults in CA also move with greater frequency causing the strata around them to be splintered with spiderweb cracking, making them easier to move when pressure builds up. The New Madrid fault doesn't move much because it is not along a significant induction/subduction area between plates like those in CA (though the plates on the coast are not actually diving under one another but rather rubbing against each other). This is why the last major quake at New Madrid was so large. There's very little movement to reduce the strain.