Microseismicity associated with the Hebron Fault in SW Namibia – a case study of earthquake clusters in stable continental regions
| Autor: | Whitehead, Benjamin, Sloan, Alastair, Quiros, Diego, Salomon, Guy, Kahle, Beth, Kahle, Richard, Muir, Robert |
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| Jazyk: | angličtina |
| Rok vydání: | 2023 |
| Zdroj: | XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) |
| Popis: | The Hebron Fault lies within southwestern Namibia, a stable continental region. It features a prominent northwest-trending scarp which displaces Quaternary alluvial fans and channels. The scarp has a length of 45 km, a maximum height of 10.1 m and an average height of 5.9 m. Fault scaling relationships suggest the scarp formed in 2–5 events of Mw ~7. Interestingly, geomorphological analyses only found evidence for a single event. In common with other major paleoseismic fault scarps in southern Africa, no earthquake cluster is recorded near the Hebron Fault in regional catalogues. In order to investigate the possibility of missed low-magnitude seismicity, below the detection threshold of the regional networks, a network of 23 4.5 Hz three component geophones was installed around the Hebron fault scarp. Earthquakes were identified using a STA/LTA coincidence trigger and P and S wave arrivals were manually picked. More than 200 earthquakes were located near the Hebron Fault with Ml ≤ 3.6 to a maximum depth of 20 km. A regression through the hypocentres results in a plane corresponding to the expected fault plane. Observed earthquakes at the Hebron Fault may either represent a long-lived aftershock sequence or a form of background seismicity associated with the fault.The fact that the earthquake cluster associated with the Hebron Fault was missed by regional networks suggests that seismic hazard can be overlooked, particularly in stable continental regions where seismic networks are often not well developed and the repeat-times of large earthquakes are longer than the instrumental record. The 28th IUGG General Assembly (IUGG2023) (Berlin 2023) |
| Databáze: | OpenAIRE |
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