Hi EQF. Maybe there was mining in the area and maybe there wasn¡¯t. You have contacts in China so why don¡¯t you find out. Ask them if the mines had any affect on why they weren¡¯t able to predict the quake. You might also ask them how many other predictions they haven¡¯t made and why. A couple of times a year they have a quake where destruction and deaths occur, but you almost never hear them saying that a warning was issued and the village or town was evacuated.

There were precursors to the Tangshan quake, if you want to call them that. I can assure you though that I would not want to try and take it the bank. Take Care¡­Don in creepy town

The statistics show that there occurred one earthquake of M=8.5, five of M=8, and twelve of M=7-7.9 in North China from 1000 AD to the present. The occurrence frequency is not high but the earthquakes were quite large. Figure 1 shows the magnitude distribution of historical earthquakes over time in North China. It can be seen in the figure that there were four active periods for large earthquakes in North China: in the first active period (1011-1076) earthquakes mainly occurred in the Shanxi and the North China plain belt; in the second period (1290-1368) earthquakes mainly concentrated in the Shanxi belt; in the third period (1484-1730) earthquakes were distributed in all of the four belts; in the fourth period (1815-present) earthquakes mostly concentrated in the North China plain, the northern part of the Liaoning-Shandong belt and the Yinshan- Yanshan belt (Fig. 2).

Another feature of strong earthquake activity in North China is the time interval
between two adjacent active periods which is comparatively long, more than 100 years
generally. Within an active period strong earthquakes often occurred in clusters and the
time of occurrence was quite concentrated. For example, there occurred five earthquakes
of M¡İ8 in North China during the third active period which lasted for 246 years, and
three of them occurred within 27 years from 1668-1695; this feature became more clear
in the fourth active period. From 1815 to 1980, there occurred seven earthquakes of
M=7-7.8, and four of them occurred within 10 years from 1966-1976. The 1966 Xingtai
earthquake marked the beginning of the highest seismic activity in North China during
the fourth active period, and the Tangshan earthquake was the most conspicuous event
within this period.

http://caltecheerl.library.caltech.edu/archive/00000353/01/Tangshan/Volume1_Chapter_1.pdf

• Tangshan Earthquake