Act of nature.
The earthquake triggered the tsunami
An earthquake.
An earthquake happened, which triggered the tsunami.
It created the tsunami.
It was triggered by an earthquake.
You can't predict earthquakes
The tsunami was triggered by an earthquake.
An earthquake
Samoan crisis happened in 1887.
8.1 moment magnitude
The earthquake that caused the tsunami was on the same day, 29 September, 2009.
Samoan Clipper happened on 1938-01-11.