During a disastrous earthquake, the early assessment and timely reporting of the peak ground acceleration (PGA) and peak ground velocity (PGV) maps will be crucial in an effective emergency response operation. In this study, we first derive an empirical relationship between ML and MW. The PGA and PGV attenuation relationships are deduced with data from the Taiwan Strong Motion Instrumentation Program (TSMIP) and the Taiwan Rapid Earthquake Information Release System (TREIRS). Site corrections of the attenuation relationships for shallow and large earthquakes in Taiwan region are also obtained. Peak values of earthquake strong ground motion can be well determined in Taiwan as soon as the earthquake location is determined, and magnitudes are calculated by the TREIRS. This peak ground motion value information can be immediately turned into the calculated PGA and PGV maps that can be issued within two minutes of the earthquake origin time. During any disastrous earthquake, these maps are found to be very useful for immediate seismic damage assessment and dispatching of emergency response missions.