The Ordos Block, surrounded by numerous active faults, is a relatively rigid but dangerous area with many strong historical earthquakes. We derive the block rotation velocity and fault slip rates in this area by using GPS data recorded from 1999 to 2007 and implementing an elastic block model. Instead of assuming vertical faults, as did most previous studies in and around Ordos, we use an improved method to invert for the fault dip angles and construct a closed 3-D fault system in our inversion. The predicted slip rates range from <1 mm/yr to ~ 10 mm/yr. Our results are roughly consistent with geological and other geodetic observations. Using the estimated slip rates, we also calculate the cumulative seismic moment due to fault locking and the released moment from historical earthquake catalogues. A comparison of the two quantities indicates that the Hetao Rift has an unreleased seismic moment equal to a Mw 7.9 earthquake, which is also indicated by frequent earthquakes above M6 after 1900.
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机译：鄂尔多斯地块被众多活动断层包围，是一个相对刚性但危险的地区，有许多强烈的历史地震。我们利用1999年至2007年记录的GPS数据并实现了弹性块模型，得出了该区域的块旋转速度和断层滑动率。像鄂尔多斯及其周边地区以前的大多数研究一样，我们没有采用垂直断层的方法，而是使用一种改进的方法对断层倾角进行反演，并在反演中构造了一个封闭的3-D断层系统。预计的滑移率范围从<1 mm / yr到〜10 mm / yr。我们的结果与地质和其他大地观测基本一致。使用估计的滑移率，我们还计算了由于断层锁定而产生的累积地震矩以及历史地震目录中的释放矩。这两个数量的比较表明，河套裂谷的未释放地震矩等于7.9 Mw地震，这也由1900年以后M6以上的频繁地震所表明。
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