自然通讯纸(提示2011年日本东北部大地震引起的重力信号][1]提出了一种“…报告搜索提示重力信号在2011 Mw 9.0日本东北部大地震的破裂在数据记录由超导重力仪在附近地下观测站和五个宽带地震检波器的日本网络F-net。”They conclude that with a certainty of about 99% that a prompt gravity signal was detected. The change in position of large masses of crust resulted in a tiny change in gravity even 500 km away and this was within detectable limits of this extremely sensitive instrument. Since gravity's influence "travels" at the speed of light it is suggested this might be an avenue to be explored for a potential early warning system. Considering that electrical and optical signals (e.g. the internet or radio or a more dedicated communications system) travel about 2/3 the speed of light in wires and fiber, and even conventional internet pings are of the order of 100 milliseconds or better, *is there any suggestion or discussion anywhere else besides this paper* that super-sensitive gravimeters would be in any way better and/or cheaper than a network of cheap sensors? In either case the idea is an early warning for something "big" rather than accurate measurements. I'm just thinking that although the paper and analysis is interesting and elegant - is there any serious discussion or speculation that this could somehow be useful as an early warning system? [1]: http://www.nature.com/articles/ncomms13349