The length of Evans et al. (2003) necessitated transfer of several less germane sections to this alternate forum to meet that venues needs. These sections include a description of the development of Figure 1, the plot of spatial variability so critical to the argument for dense arrays of strong-motion instruments; the description of the rapid, integer, computational method for PGV used in the TREMOR instrument (the Oakland instrument, the commercial prototype, and the commercial instrument); siting methods and strategies used for Class B TREMOR instruments and those that can be used for Class C instruments to preserve the cost advantages of such systems; and some general discussion of MEMS accelerometers, including a comparative Table with representative examples of Class A, B and C MEMS devices. (MEMS means Micro-ElectroMechanical Systemsmicromachined sensors, generally of silicon. Classes A, B, and C are defined in Table 1.)