M7.8 Flores earthquake damages nearly 99,000 homes in Indonesia
A shallow thrust quake off Flores on 15 August killed about 130 people and damaged close to 99,000 houses, with a small tsunami.
A magnitude 7.8 earthquake struck off the north coast of Flores in eastern Indonesia early on 15 August 2026, according to the US Geological Survey. By 4 September, Indonesia's disaster agency counted 129 deaths and 98,986 damaged houses, Metro TV News reported. More than 111,000 people were still in shelters three weeks after the shaking.
- 129deaths counted by BNPB on 4 September
- 111,321people still in shelters on 4 September
- 1.61 mmaximum tsunami height, recorded at Reok
- 1.7 millionpeople exposed to strong to severe shaking, USGS estimates
- 95%of houses that collapsed in Nepal in 2015 were low-strength masonry
What happened
The earthquake struck at 05:58 local time on 15 August 2026, which was still 14 August in UTC time. The US Geological Survey (USGS) lists it at magnitude 7.8, about 66 km north-northwest of the town of Ende, at a shallow depth of about 10 km. Indonesia's geophysics agency, BMKG, measured it at magnitude 7.7. Both agencies describe a reverse, or thrust, fault, where one block of rock is pushed up over another.
The USGS issued an orange alert in its PAGER system, which estimates likely deaths and economic losses soon after an earthquake. Its summary says about 1.7 million people were exposed to strong to severe shaking. BMKG reports that the worst-hit areas included the districts of Sikka, Nagekeo and Manggarai. Damage was recorded to homes, schools, health facilities, government offices and transport links.
A tsunami followed. The USGS impact summary lists a maximum wave height of 1.61 m at Reok in Manggarai, 0.94 m at Maurole in Ende, and smaller waves farther away. It also reports that landslides damaged 3,614 buildings and three roads, and that power was cut in parts of East Nusa Tenggara province.
On 4 September, the national disaster agency BNPB gave updated figures, reported by Metro TV News. It counted 129 deaths from direct and indirect effects, 1,723 injured, 98,986 damaged houses and 111,321 people still in shelters. BNPB said teams were checking hospitals and schools to decide whether they were safe to use again, and that tent schools were being set up so children could keep studying.
The engineering behind it
The USGS explains the setting. The Australian plate moves north against the Sunda plate at about 69 mm per year, and the two meet at the Sunda Trench, about 350 km south of this earthquake. This event happened on a thrust fault inside the overriding plate, north of Flores. BMKG links it to the Flores back-arc thrust, an east-west fault with a long history of damaging earthquakes. Since 1950, the USGS counts 37 other earthquakes of magnitude 6 or larger within 250 km.
The USGS also notes that an earthquake of this size is not a point. It is slip over a large area of fault, typically about 90 km long and 45 km wide for a reverse fault event of this magnitude. A shallow rupture that close to the coast explains both the strong shaking on land and the tsunami. In 1992, a magnitude 7.8 earthquake only 63 km away caused a tsunami and at least 2,500 deaths.
Most of the damage was to houses. In general engineering terms, small houses built with stone, brick or concrete block walls are heavy and stiff, but weak when shaken from side to side. If the walls are not tied together at the corners and at floor and roof level, they can crack, separate and fall outward. Well-designed houses use horizontal bands, vertical reinforcement at corners and openings, and good mortar to hold the walls together.
PAGER works by combining a map of estimated shaking with data on where people live and how buildings in that region usually perform. For this earthquake, the USGS model gave the highest chance, about 43 percent, to a death toll between 100 and 1,000. The count BNPB reported on 4 September, 129, falls inside that range. Fast estimates like this help governments and aid groups decide how much help to send before full reports arrive.
What it means in Nepal
Nepal's own experience shows the same pattern. The government's Post Disaster Needs Assessment after the 2015 earthquake recorded 498,852 houses fully collapsed or damaged beyond repair and 256,697 partly damaged, across 31 districts. Of the collapsed houses, 474,025, or 95 percent, were low-strength masonry. The assessment found that most damaged buildings were old constructions in mud mortar, without adequate earthquake-resistant detailing.
The same assessment described the typical failures. Parapets and gable walls toppled, walls fell outward, wall corners separated, and floors and roofs collapsed when the walls holding them up failed. It also noted weak enforcement of the Nepal National Building Code, including in municipal areas where compliance was required, and recommended that the code's mandatory rules of thumb for small buildings be put into practice.
The assessment also looked at reinforced concrete buildings, which made up 15 percent of buildings in the affected districts. Their damage came mainly from a lack of strength and ductility, the ability to bend without breaking. It listed soft storey collapse, where one weak floor fails, as well as failed beam-column joints, cracked columns and poor workmanship. For rebuilding, it pointed to the seismic rules in the national code, such as NBC 105.
The Flores figures repeat this lesson in another country. Earthquake safety is not only about tall buildings. It depends heavily on ordinary houses built with limited engineering input. After an earthquake, buildings such as schools and hospitals must also be inspected quickly and classified as safe, restricted or unsafe, as Indonesian teams were doing in September. That work needs engineers who can read cracks and judge whether a structure can still carry its loads.
What to study if this interests you
Engineering Geology I, ENCE 102, in the first semester of BCE, introduces plates, faults and earthquakes. Building Technology, ENCE 255, in the fourth semester, covers how houses are built, including walls, bands and connections. Design of Timber and Masonry Structures, ENCE 301, in the fifth semester, teaches how masonry walls carry loads and how to make them earthquake-resistant. Design of RCC Structures, ENCE 352, in the sixth semester, covers reinforced concrete design, including detailing for earthquake loads.
Words in this story
- Thrust fault
- A fault where one block of rock is pushed up and over another as the crust is squeezed.
- PAGER
- A USGS system that quickly estimates likely deaths and economic losses after a major earthquake.
- Low-strength masonry
- Walls of stone, brick or block laid in weak mortar such as mud, without reinforcement.
- Mandatory rules of thumb
- Simple building rules in Nepal's code for small houses that are not designed by an engineer.
Where this comes from
- BMKG (Indonesian Agency for Meteorology, Climatology and Geophysics), 21 Aug 2026
- Metro TV News, 4 Sep 2026
- USGS, 15 Aug 2026
- Government of Nepal, Nepal Earthquake 2015 Post Disaster Needs Assessment, Vol. B (hosted by ILO), 1 Jun 2015
Written in our own words; no sentence is copied from these reports. Researched with AI assistance on 11 October 2026; no member of faculty has reviewed it yet. If you spot a mistake, call 01-5091616 and we will correct it and say so.
