1881 Nicobar Islands earthquake
... that the magnitude of the 1881 Nicobar Islands earthquake has been estimated with records from tide gauges set up by the Great Trigonometric Survey?
... that the magnitude of the <b id="mwBsU"><a href="./1881_Nicobar_Islands_earthquake" id="mwBsY" rel="mw:WikiLink" title="1881 Nicobar Islands earthquake">1881 Nicobar Islands earthquake</a></b> has been estimated with records from tide gauges set up by the <a class="mw-redirect" href="./Great_Trigonometric_Survey" id="mwBsc" rel="mw:WikiLink" title="Great Trigonometric Survey">Great Trigonometric Survey</a>?