Giuseppe Mercalli combined earthquake intensity scales to develop his own that came to be known as the Mercalli Scale. Later, Charles F Richter developed a magnitude scale to measure earthquakes. His scale was used for decades. Now, there is a modified Mercalli scale with twelve levels that most scientists use. The most common earthqaukes fall into the first two levels, and may not be noticed by most people. Buildings will rarely suffer damage before level seven, though they speed up quickly from there. And continued large quakes without repairs may cause damage at lower levels.
In my novels, Trails 1: Trails Through the Fault Lines and Trails 2: Trails Through the Volcano, the scientist Dr. Rebecca explains the switch to the Modified Mercalli Scale, and how the accumulated affects will affect buildings. The people in the novel show the frayed nerves and behaviors of those who suddenly undergo frequent noticeable quakes.
The Severity of an Earthquake. USGS. http://pubs.usgs.gov/gip/earthq4/severitygip.html. Accessed Date: 08/13/16. Publication Date: Friday, January 11, 2013.