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.

印尼苏门答腊岛北部出现的8.6级地震，并未像该国2004年灾难那样，导致海啸发生。探索新闻网的一篇报道揭示了诸多原因。

本次地震是沿着海洋转换断层带发生的，将海底平面慢慢滑开，而不是让其突然断裂。

让其滑开的运动含有较少的能量，不会使整个海平面上升太多。因此也就不太可能造成2004年印尼海啸或2011年日本海啸那样的巨浪。

新加坡地球观测研究所所长凯利·西向路透社表示，此次的海下大地震乃两千年一遇，该地区发生毁灭性地震的风险加大。

他说：“这是记录在册的最大的走滑型地震，其余震也是我们所知的第二大余震。”

据介绍，在走滑型地震中，相互碰撞的板块发生了水平运动。这种类型的地震比板块发生垂直运动的地震的威力要小，也不太可能引发大的海啸。