Malawi

Malawi is one of the most seismically active countries in southern Africa, owing to its position along the Malawi Rift — the southernmost section of the East African Rift System's western branch. Lake Malawi (also called Lake Nyasa), which dominates the eastern portion of the country, occupies one of the deepest rift basins in the world, with a water depth exceeding 700 metres and a sediment fill beneath that extends several kilometres further. The lake basin is bounded by major active normal [[fault]]s on both sides, and these faults generate frequent moderate-to-large earthquakes that affect the country's lakeside communities.

The Livingstone Fault on the northern margin of the Malawi Rift has the longest continuous fault scarp in the East African Rift — a linear escarpment rising more than 2,000 metres above the rift valley floor. Geomorphological evidence suggests that this fault has ruptured repeatedly in large magnitude events during the Holocene, though the return period for the largest events may be thousands of years. The Bilila-Mtakataka Fault on the western margin of the central lake basin is another major seismogenic structure.

The most significant earthquake in Malawi's recorded history struck on 10 March 1989 near Salima on the western shore of Lake Malawi, with a [[magnitude]] of 6.6. The earthquake killed at least 9 people and injured hundreds. It caused widespread structural damage in Salima and Lilongwe, where many buildings collapsed or were rendered uninhabitable. The [[epicenter]] was located on the Bilila-Mtakataka Fault system, and field investigations documented a surface rupture trace extending for approximately 100 kilometres — one of the longest surface ruptures recorded for a magnitude 6.6 earthquake, suggesting that the fault had a long seismic gap before the 1989 event.

In January 2017, a sequence of earthquakes struck the northern end of Lake Malawi near Karonga. A magnitude 5.9 main shock was followed by numerous [[aftershock]]s over several weeks. Earlier, in December 2009, a devastating earthquake sequence struck Karonga directly, beginning with a magnitude 5.8 event on 6 December followed by a magnitude 6.0 event on 19 December. The latter event killed 4 people, injured over 300, and destroyed or seriously damaged approximately 3,000 buildings in Karonga town. The sequence highlighted the vulnerability of the largely unreinforced masonry construction typical of Malawian towns to even moderate shaking.

The palaeoseismic record preserved in the sediments of Lake Malawi is extraordinary. Because the lake has been continuously filled for millions of years, its sediments contain an unbroken archive of past earthquakes detectable as mass transport deposits (underwater landslides triggered by shaking) interbedded with normal lacustrine sediments. Sub-bottom profiling and sediment coring from the lake have identified multiple large-magnitude events (estimated M > 7.0) over the past 100,000 years, confirming that the Malawi Rift is capable of generating very large earthquakes far exceeding anything in the historical record.

The [[seismic-wave]] pattern in Malawi shows clear normal-faulting mechanisms consistent with the extensional regime, with fault planes oriented roughly north-south parallel to the rift. Extension rates in the Malawi Rift are estimated at approximately 2 to 3 millimetres per year. The depth of seismicity is predominantly in the upper 20 kilometres of the crust. The [[epicenter]]s cluster along the western lake margin faults and at the northern and southern terminations of the lake basin, where the rift geometry changes.

The tectonic framework involves the separation of the Nubian and Somalian plates along the western rift branch, with Malawi sitting on the boundary between these two sub-plates. The Precambrian basement flanking the rift consists of Mozambique Belt high-grade metamorphic rocks — ancient terrain that was deformed during the assembly of the supercontinent Gondwana approximately 550 million years ago and now forms the rigid walls of the rift basin.