And then there are the M-Disk: http://www.extremetech.com/computing/92286-m-disc-is-a-dvd-made-out-of-stone-that-lasts-1000-years. USD DOD test: http://www.mdisc.com/uploads/M-DISC_1sheet_ChinaLake_vF.pdf. Down side, requires writer that is M-Disk capabale, and disk are expensive (ie about 3 bucks per disk.
The Shaanxi earthquake's epicenter was in the Wei River Valley in Shaanxi Province, near the cities of Huaxian, Weinan and Huayin.
After the Haicheng earthquake of February 1975, earthquake swarms and moderate earthquakes occurred frequently in northern China at Miaodao in Shandong Province, Horinger in Inner Mongolia, Daichen (170 km southwest of Tangshan) in Hebei Province, and Taiyuan in Shanxi Province.nsufficient research on seismogenic structures of this region was the main cause of the difficulties in the assessment of seismic risk of the Tangshan region before the great earthquake of 1976. Tectonic conditions play an important role in the assessment of seismic risk.