Research on the earthquakes in early Eastern Han Dynasty

The historical literatures of earthquakes in early Eastern Han Dynasty (AD 25—127) are valuable. They reflect the transfer-process of earthquake documentary from scattered and nonsystematic records in early years to continuous records and being understood gradually. The documented earthquake events in this period are rather plentiful. However, the relevant information about these earthquakes has not been studied deeply and the parameters of few earthquakes in this period have been obtained so far. The existing investigations show that the reporting manners in this period are mainly expressed as “Junguo earthquake” and “Capital area earthquake”. The documented events occurred mainly in the region of the Great North Chinaafter He Emperor of Han Dynasty. In this paper, a new relationship of seismic intensity attenuation is used. By means of the intensity-magnitude table in Earthquake Catalogue of China, the earthquake parameters in this period are evaluated following the conceptions of Junguo-average geographic area and seismic felt area. In the light of earthquake example standard, 33 earthquake events in early Eastern Han Dynasty are analyzed particularly. The most important events in the studied period are four strong earthquakes with magnitude ≥6 ¹/₂ , i.e. , the Nanyang earthquakes in October of AD 46 and March of AD 119, the south Hebei-West-Shandong earthquake in October of AD 121 and the Hanyang earthquake in May of AD 123; their aftershocks all occurred in 1—2 years. On the other hand, the earthquake events before AD 118 distribute principally in the Great North China, and their epicentral distances from the capital Luoyang are all larger than 200 km. Except for the two events with magnitude of 5 ¹/₂ —6, all the others are of moderate magnitude of 5—5 ¹/₂ . Though the capital Luoyang underwent many earthquakes, it has not subjected to destructive or medium catastrophes. The effects caused by these earthquakes in this period are not strong and they are basically seismically felt or strong felt events.