BMKG analysis of the M 6.9 Moroccan earthquake: shallow crustal earthquake, similar to the 1755 event

TIME.CO, Jakarta – The Agency for Meteorology, Climatology and Geophysics or BMKG provides analysis of earthquake tectonics of magnitude 6.9 Saturday 9 September 2023 at 05.10.59 WIB in the territory of the country Morocco. The epicenter of the earthquake was located at the coordinates 31.01° north latitude and 8.46° west longitude, precisely on terrain with a very shallow hypocenter depth of 28 kilometers.

“This 6.9 magnitude earthquake is the major and largest earthquake ever recorded in history to ever occur in Morocco,” wrote the head of the Earthquake and Tsunami Center BMKG Daryono in his statement.

Recent reports indicate that the earthquake caused damage and resulted in casualties.

Daryono explained that the earthquake paid attention to the location of the epicenter and the depth of the hypocenter: “The earthquake that occurred was a type of shallow crustal earthquake due to active fault activity in the Atlas Mountains area, in Morocco”.

The morphology of this mountain range runs southwest to northeast from Agadir to Aït Ahmadou Haddou, Morocco.

The results of the source mechanism analysis carried out by BMKG show that the earthquake that occurred had an upward motion or source mechanism thrust defect, which reflects the compression forces that occurred in the tectonic zone at the origin of the earthquake. This earthquake occurred in an area of ​​the active fault earthquake source path that has been mapped, however, this area is known for its history of relatively low seismicity.

Earthquake impact

This earthquake had a very destructive impact, reaching the intensity scale VII – IX MMI, causing damage and deaths in the Old City of Marrakech. Marrakech is the fourth largest city in Morocco and is one of the largest population centers.

Announcement

Marrakech suffered the most severe damage because it was close to the source of the earthquake, combined with the presence of old buildings vulnerable to collapse due to seismic tremors because their structures were already weak.

The main cities affected by the strong seismic tremors around Marrakech were Ouarzazate, Essaouira, Safi, Agadir, Casablanca and Errachidia. Not only in Morocco, this shallow earthquake was felt in a very large area, including neighboring countries, such as Portugal, Spain and Algeria.

Another story of earthquakes

The M6.9 magnitude Marrakesh earthquake that caused fatalities is reminiscent of the devastating M5.8 magnitude earthquake that shook Agadir, Morocco on February 29, 1960. Although the earthquake’s magnitude was relatively small, the earthquake that damaged Agadir killed more than 10,000 people and became the deadliest earthquake in Morocco’s history.

The current Marrakesh earthquake of magnitude 6.9 is comparable in magnitude to the historic destructive earthquake that destroyed the city of Meknes with magnitude of 6.5 – 7.0 which occurred on November 27, 1755. This earthquake killed thousands of people because it struck a mountainous region with many settlements rural and small towns that have many vulnerable buildings with weak structures. Apart from that, the strong earthquake occurred at night, at 11pm local time, when all residents were at home.

As of 16:25 WIB, monitoring results showed that several aftershock activities had occurred with a significant aftershock of magnitude M4.9 at 05:30 WIB which was felt on the VI MMI intensity scale .

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