Scientists from Indonesia’s Meteorology and Geophysics agency said it could have been caused by undersea landslides from the eruption of Anak Krakatau, a volcanic island formed over years from the nearby Krakatau volcano. They also cited tidal waves caused by the full moon.
Footage posted on social media showed a pop band named “Seventeen” performing under a tent on a beach as dozens of people sat listening at tables covered in white cloths. As bright strobe lights flashed on stage, a child could be seen wandering through the crowd. Then, in between songs with the drummer pounding, the stage suddenly heaved forward, throwing the band and all their equipment into the audience.
The band released a statement saying their bass player and road manager were found dead, while four other members of their group remained missing.
“The tide rose to the surface and dragged all the people on site,” it said. “Unfortunately, when the current receded our members are unable to save themselves while some did not find a place to hold on.”
Tourists were also affected during the holiday weekend ahead of Christmas.
“I had to run, as the wave passed the beach and landed 15-20m (meters) inland,” Norwegian Øystein Lund Andersen wrote on Facebook. He said he was taking pictures of the volcano when he suddenly saw a big wave come toward him.
“Next wave entered the hotel area where I was staying and downed cars on the road behind it. Managed to evacuate with my family to higher ground trough forest paths and villages, where we are taken care of (by) the locals. Were unharmed, thankfully.”
The worst affected area was the Pandeglang region of Banten province in Java, which encompasses the Ujung Kulon National Park and popular beaches, the disaster agency said. Of the deaths, 33 were in Pandeglang.
In the city of Bandar Lampung on southern Sumatra, hundreds of residents took refuge at the governor’s office.
Alif, a resident in Pandeglang district who goes by one name, said told MetroTV station that many people were still searching for missing relatives.
The Anak Krakatau volcano in the Sunda Strait that links the Indian Ocean and Java Sea erupted about 24 minutes before the tsunami, the geophysics agency said.
The 305-meter (1,000-foot) -high volcano, about 200 kilometers (124 miles) southwest of capital Jakarta, has been erupting since June. In July, authorities widened its no-go areas to 2 kilometers (1.24 miles) from the crater.
Gegar Prasetya, co-founder of the Tsunami Research Center Indonesia, said the waves were likely caused by a flank collapse — when a big section of a volcano’s slope gives way. He said it’s possible for an eruption to trigger a landslide above ground or beneath the ocean, both capable of producing a tsunami.
“Actually, the tsunami was not really big, only one meter,” said Prasetya, who has closely studied Krakatau. “The problem is people always tend to build everything close to the shoreline.”
Physical losses included 430 heavily damaged homes, nine heavily damaged hotels and 10 heavily damaged vessels. Footage posted by the head of the disaster agency showed the aftermath of flooded streets and an overturned car.
In September, more than 2,500 people were killed by a quake and tsunami that hit the city of Palu on the island of Sulawesi, which is just east of Borneo.
In December 2004, a massive magnitude 9.1 earthquake off Sumatra island in western Indonesia triggered a tsunami that killed 230,000 people in a dozen countries. Indonesia is a vast archipelago of more than 17,000 islands home to 260 million people. Roads and infrastructure are poor in many areas, making access difficult in the best of conditions.