Earthquake in Ghana and Togo in 1906

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The earthquake in Ghana and Togo in 1906 occurred on November 20, 1906 in the coastal and coastal regions of the eastern Gold Coast and the western Mina Coast. The epicenter of this earthquake was at Ho , near Accra . The numerous aftershocks, which mainly occurred in the 48 hours following the main earthquake, but which lasted until the end of February of the following year, had their focus in the region between Ho, Misahöhe and Kpong . The intensity was classified according to the observed effects on level VIII of the Modified Mercalli Scale, the magnitude calculated from this was 5.

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Accra was shaken on November 20, 1906 at around 9:00 p.m. local time by a violent quake lasting about 30 seconds. According to the reports available, the houses are said to have moved "like aspen leaves" and numerous houses were cracked. According to contemporary witnesses, it is said to have been the strongest earthquake in this region since 1862, when, for example, the city of Accra was almost completely destroyed by an earthquake.

Several tremors were also noted in Sekondi-Takoradi (175 km as the crow flies southwest of Accra) .

At around 9.15 p.m. Lomé was shaken by a first quake lasting about 5 seconds, which was followed 21 minutes later by a second, but weaker, shaking of less duration. The intensity of these tremors is classified by contemporary witnesses according to the Rossi-Forel scale for Lomé at about 3. Noises are said to have occurred that are reminiscent of the rolling of large barrels or the thunder of a distant thunderstorm.

Further inland, however, the earthquake effect was far stronger. In Assahun , one observer speaks of the violent trembling of the buildings, while in Palimé and Misahöhe, an even swaying of the earth's surface lasting about 10-15 seconds was observed. 21.5 minutes later, a second, weaker quake of shorter duration was registered here.

The tremor seems to have had the greatest intensity in the area around Ho . The tremor was expressed there in two strong shaking of the ground, which was accompanied by a strong thundering and roaring noise. Strangely enough, the second thrust is said to have been the stronger one.

Also in the east of what was then Togo, such as For example, in Anecho or Tokpli on the Mono River , weak vibrations were perceived, also in Atakpamé , while in Sokodé and further north no more tremors were noticeable. No tremors were felt in Kete Krachi am Volta either.

Aftershocks

Up to November 22, 1906, 15 more tremors, albeit less intense, were registered.

On December 2, 1906, another aftershock occurred, which was felt in Palimé at around 4 a.m. local time. The strength of the tremors is said to have been similar to the earthquake of November 20, 1906.

Spread

The earthquake of November 20, 1906, was observed on the Gold and Mina Coast over a coastline 350 km long and inland about 200 km wide.

During the earthquake of November 20, 1906 (at least in the interior of Togo), the bumps ran in the direction from northwest to southeast, while the waves during the earthquake of December 2, 1906 in Palimé spread from northeast to southwest.

Cause of local tremors

The earth tremors described are tectonic earthquakes caused by shifts in the earth's crust . In this section of the West African coast, such shifts take place preferentially in the region where the extension of the Akwapim-Togo mountain range near Accra reaches the coast and is cut off here by powerful faults against the oceanic crust running approximately in an east-west direction becomes. Similar east-west fault lines should also play a major role in the mountain building of the southern Togo Mountains. These faults are also characterized by geologists as "relatively young" faults, where displacements preferably accompanied by earthquakes occur.

The fact that the bumps continued to build up into the interior of the country in places during this quake can be explained by the geological substructure of these regions. While the coastal areas in a width of approx. 30 to 45 km inland consist very deep of loose, sandy and clayey material, which transmits the earthquake waves very poorly, rocky subsoil begins almost everywhere behind them, where an earthquake wave can propagate much better. This also explains the fact why the intensity of the tremors in this quake was far stronger in the more distant interior than in the coastal areas closer to the epicenter.

See also

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  • Koert: Togo during the last Accra earthquake. In: Official Journal for the Protected Area Togo , 2 (5), 1907, pp. 56–57
  • Koert: Togo during the last Accra earthquake. In: Communications from the German Protected Areas , 20 (2), 1907, p. 122
  • H. Limbrock: Earthquake of December 2, 1906. In: Official Journal for the Protected Area Togo , 2 (12), 1907, p. 90

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Coordinates: 6 ° 30 ′ 0 ″  N , 0 ° 18 ′ 0 ″  E