1990 South Sudan earthquakes

Earthquake sequence in South Sudan August 2026 5.121 32.145 South Sudan#Africa South Sudan#Africa 4.8594 31.5713 100 Juba left Green pog.svg South Sudan#Africa 5.121 32.145 Bullseye1.png 40 260 right yes 20 May 1990 to 9 July 1990 Strike-slip & Normal South Sudan Yes VIII 1990-05-20 02:22:01 1990-05-24 19:34:44 1990-05-24 20:00:08 1990-07-09 15:11:20 04:22:01 21:34:44 22:00:08 17:11:20 usp00049hf usp00049q9 usp00049qe usp0004bkr 7.2 w yGaulon Chorowicz Vidal Romanowicz 1992 96 6.5 w y 7.1 w y 6.6 w yAmbraseys Adams 1991 369792 370208 370216 362203 31 dead Between 20 May and 9 July 1990, present day South Sudan was rocked by a series of violent earthquakes. It started with the largest event (w 7.2), and continued with multiple very large aftershocks for the next couple of months. The earthquake sequence ruptured over a length of 50 km on. It contains some of the largest recorded earthquakes anywhere in Africa. Tectonic setting The East African Rift System (EARS) is a system of rifts and associated rift lakes within the eastern portion of the African continent. It accommodates the internal breakup of Africa. It is a boundary between the Somali and African plate. The Victoria and Rovuma microplates help accommodate additional more local stresses. The eastern portion of the rift runs from the Afar rift to Tanzania, while the western portion runs from Lake Albert (Africa) in Uganda all the way down to Mozambique.Gaulon Chorowicz Vidal Romanowicz 1992 The Aswa Rift Zone (ARZ) is an important geologic structure in the area near the earthquakes. The ARZ may act as a broad zone of faulting that links together the eastern and western portions of the EARS.Giardini Beranzoli 1992 The mainshock occurred along a fault where the ARZ and EARS meet.Mulwa Kimata 2014 Earthquake sequence 20 May mainshock The first and largest earthquake in the sequence struck near Juba at 02:22:01 on 20 May 1990. The event had a b of 6.5-6.7, s of 7.1-7.4, and w of 7.2, and struck at a depth of 7-15 km on.b 6.5Girdler McConnell 1994 68-b 6.7Moussa 2008 90s 7.1-7.4Giardini Beranzoli 1992 106w 7.2Gaulon Chorowicz Vidal Romanowicz 1992 967 km depthMulwa Kimata 2014 493-15 kmAmbraseys Adams 1991 399 Its focal mechanism shows left-lateral (sinistral) strike-slip faulting, which is consistent with the shear forces in the area of the ARZ.Gaulon Chorowicz Vidal Romanowicz 1992 The earthquake ruptured over an area of 26-60 km on by 40 km on. The average slip in the rupture was 0.56-1.1 m on and it had a stress drop of 1.63-1.65 MPa.Moussa 2008 94Mulwa Kimata 2014 493 The earthquake had an aftershock length of 120 km on.Pegler Das 1996 906 The earthquake was preceded by a low-frequency slow slip signal immediately before the high-frequency main event, which could mean the event was an amalgamation of a slow and normal earthquake.Ihmle Jordan 1994 1547 The earthquake killed 31 people and damaged some buildings in Juba, and some in Moyo, Uganda. The Nile's banks had fissures, and a bridge near Torit was destroyed. The shock was felt for up to 800 km on.Ambraseys Adams 1991 398 This event is believed to be the largest earthquake ever recorded in South Sudan, and is one of the largest events known in all of Africa.Gaulon Chorowicz Vidal Romanowicz 1992 87 24 May foreshock At 19:34:44 on 24 May 1990, another large earthquake struck southern South Sudan. It occurred at a depth of 10-14 km on with a b of 6.1, s of 6.5-6.8 and w of 6.5-6.6.Gaulon Chorowicz Vidal Romanowicz 1992Mulwa Kimata 2014Ambraseys Adams 1991 By analyzing body waves, the earthquake was found to have slipped in a normal sense.Gaulon Chorowicz Vidal Romanowicz 1992 98 24 May mainshock At 20:00:08, only a little over 25 minutes after the foreshock, an even stronger earthquake struck the region: the second strongest of the whole sequence. This event was a b 6.6, s 7.0, w 7.1 earthquake that occurred at a depth of 10-40 km on.Gaulon Chorowicz Vidal Romanowicz 1992Mulwa Kimata 2014Ambraseys Adams 1991 The focal mechanism of the earthquake was normal faulting.Girdler McConnell 1994 67 It caused additional structural damage to buildings previously affected by the first and strongest shock, however, no casualties occurred. The worst damage was observed in uninhabited areas. 9 July mainshock After the sequence had largely finished, another large shock struck the area for a final time. The last big earthquake in the sequence was a b 6.0, s 6.4-6.5 and w 6.6 event. It occurred at a depth of 10-11 km on.Ambraseys Adams 1991 Focal mechanism solutions are split, with a roughly equal proportion of agencies and studies preferring a strike-slip event, with another equal proportion believing it to be a normal faulting event.Gaulon Chorowicz Vidal Romanowicz 1992 Damage The first mainshock killed 31 people and damaged buildings in Juba and Moyo, Uganda. Shaking was felt as far as Nakuru, Kenya. The mainshock of May 24 did further damage. Government buildings and private institutions were damaged in Terekeka, South Sudan. Older buildings in Juba reported cracked walls. Between 8,000 and 10,000 of the displaced required extra relief and shelter. 300,000 people were made homeless across the region as a result of the earthquakes. See also List of earthquakes in 1990 2006 Mozambique earthquake Notes References M 7.2 – 69 km ENE of Juba, South Sudan https://earthquake.usgs.gov/earthquakes/eventpage/usp00049hf/executive United States Geological Survey 28 August 2022M 6.5 – 54 km NNE of Juba, South Sudan https://earthquake.usgs.gov/earthquakes/eventpage/usp00049q9/executive United States Geological Survey 28 August 2022M 7.1 – 63 km NNE of Juba, South Sudan https://earthquake.usgs.gov/earthquakes/eventpage/usp00049qe/executive United States Geological Survey 28 August 2022M 6.6 – 60 km N of Juba, South Sudan https://earthquake.usgs.gov/earthquakes/eventpage/usp0004bkr/executive United States Geological Survey 28 August 2022ISC http://www.isc.ac.uk/cgi-bin/web-db-run?event_id=362203&out_format=ISF2&request=COMPREHENSIVE ISC-GEM 28 August 2022Significant Earthquake Database https://www.ngdc.noaa.gov/hazel/view/hazards/earthquake/event-more-info/5237 National Geophysical Data Center / World Data Service (NGDC/WDS) 1990 National Geophysical Data Center, NOAA 10.7289/V5TD9V7KSudan Earthquake May 1990 UNDRO Information Reports 1-2 29 May 1990 https://reliefweb.int/report/sudan/sudan-earthquake-may-1990-undro-information-reports-1-2 ReliefWeb 28 August 2022More earthquakes hit Sudan, 300,000 said homeless https://www.upi.com/Archives/1990/05/26/More-earthquakes-hit-Sudan-300000-said-homeless/4401643694400/ UPI 29 August 2022 Sources Ambraseys N. N. Adams R. D. Reappraisal of major African earthquakes, south of 20°N, 1900–1930 Natural Hazards December 1991 4 4 389–419 10.1007/BF00126646 129238922 https://doi.org/10.1007/BF00126646 28 August 2022 subscription Gaulon R. Chorowicz Jean Vidal Gérard Romanowicz Barbara Regional geodynamic implications of the May–July 1990 earthquake sequence in southern Sudan Tectonophysics August 1992 209 1 87–103 10.1016/0040-1951(92)90012-U 1992Tectp.209...87G https://doi.org/10.1016/0040-1951(92)90012-U 28 August 2022 subscription Giardini Domenico Beranzoli Laura Waveform modelling of the May 20, 1990 Sudan earthquake Tectonophysics 20 August 1992 209 1–4 105–114 10.1016/0040-1951(92)90013-V 1992Tectp.209..105G https://doi.org/10.1016/0040-1951(92)90013-V 28 August 2022 subscription Girdler R. W. McConnell D. A. The 1990 to 1991 Sudan Earthquake Sequence and the Extent of the East African Rift System Science 1 Apr 1994 264 5155 67–70 10.1126/science.264.5155.67 17778134 https://www.science.org/doi/abs/10.1126/science.264.5155.67 13 July 2024 subscription Ihmle Pierre F. Jordan Thomas H. Teleseismic Search for Slow Precursors to Large Earthquakes Science 2 Dec 1994 266 5190 1547–1551 10.1126/science.266.5190.1547 17841716 https://www.science.org/doi/10.1126/science.266.5190.1547 13 July 2024 subscription Moussa Hesham Hussein Mohamed Spectral P-wave magnitudes, magnitude spectra and other source parameters for the 1990 southern Sudan and the 2005 Lake Tanganyika earthquakes Journal of African Earth Sciences 2008 52 3 89–96 10.1016/j.jafrearsci.2008.05.004 2008JAfES..52...89M https://doi.org/10.1016/j.jafrearsci.2008.05.004 28 August 2022 1464-343X subscription Mulwa Josphat K. Kimata Fumiaki Tectonic structures across the East African Rift based on the source parameters of the 20 May 1990 M7.2 Sudan earthquake Natural Hazards 21 February 2014 73 2 493–506 10.1007/s11069-014-1082-y 2014NatHa..73..493M 140581505 https://doi.org/10.1007/s11069-014-1082-y 28 August 2022 subscription Pegler G. Das S. Analysis of the relationship between seismic moment and fault length for large crustal strike-slip earthquakes between 1977–92 Geophysical Research Letters 1 May 1996 23 9 905–908 10.1029/96GL00963 https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96GL00963 13 July 2024 External links M 7.2 – 69 km ENE of Juba, South Sudan – United States Geological Survey M 6.5 – 54 km NNE of Juba, South Sudan – United States Geological Survey M 7.1 – 63 km NNE of Juba, South Sudan – United States Geological Survey M 6.6 – 60 km N of Juba, South Sudan – United States Geological Survey 369792 370208 370216 362203 South Sudan earthquakes South Sudan earthquakes South Sudan earthquakes South Sudan earthquakes Category:Earthquakes in Africa South Sudan earthquakes