1999 Jiji earthquake The tremor measured 7.6 on the Moment magnitude scale, 7.3 on the Richter scale, and the focal depth was . The Central Weather Bureau recorded a total of 12,911 aftershocks in the month following the main tremor. The total energy released is estimated to be 2.1 × 10 J, approximately the same as the yield of the Tsar Bomba. The earthquake was in an unusual location for Taiwan, which experiences the majority of its earthquakes off the eastern coast, such quakes normally causing little damage. One of the aftershocks, on 26 September, was a strong earthquake in its own right,
Seismic magnitude scales times. As originally defined by m was based on the maximum amplitude of waves in the first 10 seconds or more. However, the length of the period influences the magnitude obtained. Early USGS/NEIC practice was to measure on the first second (just the first few P-waves), but since 1978 they measure the first twenty seconds. The modern practice is to measure short-period scale at less than three seconds, while the broadband scale is measured at periods of up to 30 seconds. The regional mb scale – also denoted mb_Lg, mbLg, MLg (USGS), Mn, and m – was developed by for