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The latest tectonics and the current tense state of the Aral-Ustyurt region of Uzbekistan
Новейшая тектоника и современное напряженное состояние Арало-Устюртского региона Узбекистана
- Institute of Seismology, Academy of Sciences of the Republic of Uzbekistan, Uzbekistan
Highlights
- Heat flow in the South Tien Shan fault zone: up to 70 mW/m² and more; 50–58 mW/m² to the north and south.
- Geothermal gradient up to 3.5–4.0 °C per 100 m at the Kagan, Gazli and Ispanly-Chandyr uplifts (Zunnunov et al., 1974).
- Moho depth: 40–45 km (Chardzhou step, Surkhandarya depression); 44–46 km (Kuljuktau, Zirabulak-Ziaetdin, Karatyube); up to 50 km (South Gissar).
- Jurassic thickness: 100–300 m on the Bukhara step, 1,000 m and more on the Chardzhou step.
- Present-day vertical movements: 0 to +4 mm a year in the Aral–Ustyurt region; −10 to +10 mm a year in the Fergana depression and its frame.
- Amplitude of the latest movements in the Aral–Ustyurt region: −300 to +300 m.
Keywords
- heat flow
- geothermal gradient
- South Tien Shan fault
- Aral–Ustyurt region
- Bukhara–Khiva region
- neotectonics
- active faults
Summary
Yu. M. Sadiqov, A. A. Rashidov and M. Sh. Normuminov, of the Institute of Seismology of the Academy of Sciences of Uzbekistan, describe the fault-block structure, recent movements and present-day stress of the Aral–Ustyurt region of the Turan platform. The total amplitude of the latest tectonic movements there is −300 to +300 m (600 m), and the faults that bound the Central Ustyurt swell and the West Aral uplift zone have moved by at least 600 m. Present-day vertical movements reach 0 to +4 mm a year, against −10 to +10 mm a year in the Fergana depression and its mountain frame. The region is split into the North Ustyurt and Karakum blocks by the Mangyshlak fault, the north-western continuation of the South Tien Shan deep fault.
Reviewing earlier work on the South Tien Shan fault in western Uzbekistan, the authors note that south of the fault the Moho lies at 40–45 km under the Chardzhou step and the Surkhandarya depression, at 44–46 km under the Kuljuktau, Zirabulak-Ziaetdin and Karatyube uplifts and down to 50 km in South Gissar. Heat-flow data come from wells: the fault zone stands out with heat flow of up to 70 mW/m² and more, falling to 50–58 mW/m² to the north and south, and with raised temperatures on the 1,000, 1,500 and 2,000 m depth slices. Geothermal gradients of up to 3.5–4.0 °C per 100 m are recorded at the Kagan, Gazli and Ispanly-Chandyr uplifts (Zunnunov et al., 1974). The authors link the higher heat flow to greater permeability of the crust, which may have increased the convection of gases and fluids. The Gazli earthquakes of 1976, of M 7.0 and M 7.3, occurred on this segment.
The Amu Darya flexure-fault zone forms structural steps of 1.5–2.0 km, rarely up to 4.0 km; along it runs the Godin graben, 5–7 km wide, with an amplitude of up to 500 m and more than 200 km long. The Uchbash–Karshi zone runs for more than 400 km, and across it the Jurassic thickens from 100–300 m on the Bukhara step to 1,000 m and more on the Chardzhou step; its largest Neogene–Quaternary graben is the Kokchi graben. A model of the displacement field and of the greatest horizontal stress at 15 km depth shows the region under submeridional compression, with strike-slip, reverse–strike-slip and thrust movement on the faults, and converging displacements around the Sultanuvais uplift.
How to cite
Yu. M. Sadiqov, A. A. Rashidov and M. Sh. Normuminov (2024). The latest tectonics and the current tense state of the Aral-Ustyurt region of Uzbekistan. Seysmologiya muammolari (Problems of Seismology), vol. 6, No. 2, 2024, pp. 56–65. https://seismos.uz/uploads/pdf/journal/%D0%A1%D0%B5%D0%B9%D1%81%D0%BC%D0%BE%D0%BB%D0%BE%D0%B3%D0%B8%D1%8F%20%D0%BC%D1%83%D0%B0%D0%BC%D0%BC%D0%BE%D0%BB%D0%B0%D1%80%D0%B8%202024%20%E2%84%962.pdf