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.
How Earthquakes Work. The earliest documented earthquake occurred in China in 1177 B.C. But for most of history, people didn't really have any idea what caused them -- though they had some wild theories, such as the belief earthquakes were caused by air rushing out of caverns deep in the Earth's interior.