The magnitude 8.6 earthquake that struck North Sumatra, Indonesia did not lead to a tsunami comparable to Indonesia's 2004 disaster for a couple of reasons, as said in a Discovery News story.

Today's temblor ripped along an oceanic transform fault, tearing the seafloor in a strike-slip motion as opposed to popping it apart.

Strike-slip motion carries less of an ability to push up on the entire water column above it and hence is less likely to form the same kind of tsunami wave as what hit Indonesia in 2004 and Japan in 2011.

The powerful undersea earthquake was a once in 2,000 years event and increases the risks of a killer quake in the region, Kerry Sieh, director of the Earth Observatory of Singapore, told Reuters.

"Besides it being the biggest strike-slip earthquake ever recorded, the aftershock is the second biggest as far as we can tell," said Sieh.

Strike-slip quakes involve the horizontal movement of colliding earth plates and are typically less powerful than those where there is vertical movement. They are also less likely to trigger big tsunamis.

印尼蘇門答臘島北部出現(xiàn)的8.6級地震，并未像該國2004年災(zāi)難那樣，導(dǎo)致海嘯發(fā)生。探索新聞網(wǎng)的一篇報道揭示了諸多原因。

本次地震是沿著海洋轉(zhuǎn)換斷層帶發(fā)生的，將海底平面慢慢滑開，而不是讓其突然斷裂。

讓其滑開的運動含有較少的能量，不會使整個海平面上升太多。因此也就不太可能造成2004年印尼海嘯或2011年日本海嘯那樣的巨浪。

新加坡地球觀測研究所所長凱利·西向路透社表示，此次的海下大地震乃兩千年一遇，該地區(qū)發(fā)生毀滅性地震的風(fēng)險加大。

他說：“這是記錄在冊的最大的走滑型地震，其余震也是我們所知的第二大余震。”

據(jù)介紹，在走滑型地震中，相互碰撞的板塊發(fā)生了水平運動。這種類型的地震比板塊發(fā)生垂直運動的地震的威力要小，也不太可能引發(fā)大的海嘯。