Recently, the P-wave-alert-device (P-alert) network, which is a dense array of microelectromechanical system (MEMS) accelerometers that was developed and installed by National Taiwan University for the purposes of earthquake early warnings, has recorded a large number of strong-motion records for moderate-to-large earthquakes throughout Taiwan. However, many of these stations are mounted on the vertical walls of buildings in ways such that further studies of the sensor-structure interactions on recorded acceleration data are required before the data is used in the production of high-quality shake maps. In this study, we collect the free-field accelerograms recorded by the Taiwan Strong-Motion Instrumentation Program (TSMIP) network that were operated by the Central Weather Bureau (CWB), where MEMS accelerometers were in the vicinity. Then, we compare the peak ground acceleration (PGA) ratio (R-value) between P-alert and TSMIP stations. Finally, we demonstrate how to use the R-value correction on the P-alert data, in order to rapidly produce high-resolution shake maps for relief work to be done soon after major earthquakes. At present, the shake maps produced by the P-alert network are posted automatically in real time on Facebook and are provided to the National Science and Technology Center for Disaster Reduction (NCDR) in order to allow for their relief work. These timely products provide improved information for disaster risk reduction, emergency preparedness, and emergency response.