The maximum run-up height of the 2004 tsunami near Lhoknga, Indonesia, was 51 meters. This measurement was recorded on elevated ground between Lhoknga and Leupung, on Sumatra’s western coast near Banda Aceh.
“Run-up” is not exactly the same as the height of a breaking wave offshore or at the shoreline. It describes how far above sea level tsunami water climbed on land. Surveys around Lhoknga found wave heights of roughly 30–35 meters in places, while the water reached an exceptional elevation of 51 meters on the slopes and saddleback between coastal hills.
The extreme local height resulted from several factors: the earthquake lifted the seafloor, the nearby rupture zone was close to Aceh, and the coastline’s steep hills and bay shape concentrated the incoming water. Secondary faults, known as splay faults, may also have intensified the tsunami’s height and speed.
Lhoknga was devastated, with most of its buildings destroyed. The 51-meter figure is therefore a surveyed run-up elevation, not a claim that a vertical wall of water stood 51 meters high everywhere along the coast.