Spectral P-wave magnitudes, magnitude spectra and other source parameters for the 1990 southern Sudan and the 2005 Lake Tanganyika earthquakes

Hussein, H. M.

doi:10.1016/j.jafrearsci.2008.05.004

Cited by 5 publications

(5 citation statements)

References 27 publications

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“…Changes in scarp height with a magnitude larger than the typical algorithm error (≥ 5 m) are considered to be real along-fault changes in scarp morphology. As the algorithm assumes only a single scarp surface, multi-scarps (also known as multiple scarps) or composite scarps associated with individual ruptures (Wallace, 1977;Nash, 1984;Crone and Haller, 1991;Zhang et al, 1991;Ganas et al, 2005) will be treated as a single scarp. In other words, the calculated scarp height is the cumulative vertical displacement at the surface.…”

Section: Bilila-mtakatakamentioning

confidence: 99%

“…Fault scarps developed through multiple events have been observed in many regions (Wallace, 1977;Nash, 1984;Crone and Haller, 1991;Zhang et al, 1991;Ganas et al, 2005). Multiple earthquake events have also been suggested as a method for fault development, where large faults form iteratively through fault growth and linkage of smaller fault seg- ments (e.g.…”

Section: Displacement Profile and Segmentationmentioning

confidence: 99%

“…By using the scarp geomorphology, however, a relative age between each scarp can be estimated (e.g. Nash, 1984;Stewart and Hancock, 1990;Avouac, 1993).…”

Section: Scarp Agementioning

confidence: 99%

“…Despite this, if the diffusivity constant κ is similar for each fault scarp (a reasonable assumption given the similar lithology and climatic effects on each scarp), then the relative differences in the average slope between scarps found using the TanDEM-X DEM may be used to find the relative age difference (e.g. Nash, 1984;Avouac, 1993).…”

Section: Scarp Agementioning

confidence: 99%

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A semi-automated algorithm to quantify scarp morphology (SPARTA): application to normal faults in southern Malawi

et al. 2019

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Abstract. Along-strike variation in scarp morphology reflects differences in a fault's geomorphic and structural development and can thus indicate fault rupture history and mechanical segmentation. Parameters that define scarp morphology (height, width, slope) are typically measured or calculated manually. The time-consuming manual approach reduces the density and objectivity of measurements and can lead to oversight of small-scale morphological variations that occur at a resolution impractical to capture. Furthermore, inconsistencies in the manual approach may also lead to unknown discrepancies and uncertainties between, and also within, individual fault scarp studies. Here, we aim to improve the efficiency, transparency and uniformity of calculating scarp morphological parameters by developing a semi-automated Scarp PARameTer Algorithm (SPARTA). We compare our findings against a traditional, manual analysis and assess the performance of the algorithm using a range of digital elevation model (DEM) resolutions. We then apply our new algorithm to a 12 m resolution TanDEM-X DEM for four southern Malawi fault scarps, located at the southern end of the East African Rift system: the Bilila–Mtakataka fault (BMF) and three previously unreported scarps – Thyolo, Muona and Malombe. All but Muona exhibit first-order structural segmentation at their surface. By using a 5 m resolution DEM derived from high-resolution (50 cm pixel−1) Pleiades stereo-satellite imagery for the Bilila–Mtakataka fault scarp, we quantify secondary structural segmentation. Our scarp height calculations from all four fault scarps suggest that if each scarp was formed by a single, complete rupture, the slip–length ratio for each earthquake exceeds the maximum typical value observed in historical normal faulting earthquakes around the world. The high slip–length ratios therefore imply that the Malawi fault scarps likely formed in multiple earthquakes. The scarp height distribution implies the structural segments of both the BMF and Thyolo fault have merged via rupture of discrete faults (hard links) through several earthquake cycles, and the segments of the Malombe fault have connected via distributed deformation zones (soft links). For all faults studied here, the length of earthquake ruptures may therefore exceed the length of each segment. Thus, our findings shed new light on the seismic hazard in southern Malawi, indicating evidence for a number of large (Mw 7–8) prehistoric earthquakes, as well as providing a new semi-automated methodology (SPARTA) for calculating scarp morphological parameters, which can be used on other fault scarps to infer structural development.

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Section: Bilila-mtakatakamentioning

confidence: 99%

Section: Displacement Profile and Segmentationmentioning

confidence: 99%

“…By using the scarp geomorphology, however, a relative age between each scarp can be estimated (e.g. Nash, 1984;Stewart and Hancock, 1990;Avouac, 1993).…”

Section: Scarp Agementioning

confidence: 99%

Section: Scarp Agementioning

confidence: 99%

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A semi-automated algorithm to quantify scarp morphology (SPARTA): application to normal faults in southern Malawi

et al. 2019

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“…10.1002/2017TC004628 (Figure 1a; Moussa, 2008). Nonetheless, the continual role of basement fabric in shaping the architecture of rift systems and subsequent ruptures leading to seismic events has not been fully understood.…”

Section: Tectonicsmentioning

confidence: 99%

Active deformation of Malawi Rift’s North Basin hinge zone modulated by reactivation of pre-existing Precambrian shear zone fabric

Kolawole¹,

Atekwana²,

Laó‐Dávila³

et al. 2018

Preprint

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Key Points:1. Filtered aeromagnetic data elucidates the relationship between earthquake surface ruptures and buried faults along the North Basin hinge-zone, Malawi Rift.2. Fault segments align with basement shear zone fabric.3. Strain accommodation in the North Basin hinge zone is modulated by reactivation of the underlying Precambrian shear zone fabric. Abstract:We integrated temporal aeromagnetic data and recent earthquake data to address the long-standing question on the role of pre-existing Precambrian structures in modulating strain accommodation and subsequent ruptures leading to seismic events within the East African Rift System (EARS). We used aeromagnetic data to elucidate the relationship between the locations of the 2009 Mw 6.0 Karonga, Malawi earthquake surface ruptures and buried basement faults along the hinge zone of the half-graben comprising the North Basin of the Malawi Rift. Through the application of derivative filters and depth-to-magnetic-source modeling, we identified and constrained the trend of the Precambrian metamorphic fabrics and correlated them to the three-dimensional (3D) structure of buried basement faults. Our results reveal an unprecedented detail of the basement fabric dominated by high frequency WNW- to NW-trending magnetic lineaments associated with the Precambrian Mughese Shear Zone fabric. The high frequency magnetic lineaments are superimposed by lower frequency NNW-trending magnetic lineaments associated with possible Cenozoic faults. Surface ruptures associated with the 2009 Mw 6.0 Karonga earthquake swarm aligned with one of the NNW-trending magnetic lineaments defining a normal fault that is characterized by right-stepping segments along its northern half and coalesced segments on its southern half. Fault geometries, regional kinematics and spatial distribution of seismicity suggest that seismogenic faults reactivated the basement fabric found along the half-graben hinge zone. We suggest that focusing of strain accommodation and seismicity along the half-graben hinge zone is facilitated and modulated by the presence of the basement fabric.

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Active Deformation of Malawi Rift's North Basin Hinge Zone Modulated by Reactivation of Preexisting Precambrian Shear Zone Fabric

et al. 2018

View full text Add to dashboard Cite

We integrated temporal aeromagnetic data and recent earthquake data to address the long‐standing question on the role of preexisting Precambrian structures in modulating strain accommodation and subsequent ruptures leading to seismic events within the East African Rift System. We used aeromagnetic data to elucidate the relationship between the locations of the 2009 Mw 6.0 Karonga, Malawi, earthquake surface ruptures and buried basement faults along the hinge zone of the half‐graben comprising the North Basin of the Malawi Rift. Through the application of derivative filters and depth‐to‐magnetic‐source modeling, we identified and constrained the trend of the Precambrian metamorphic fabrics and correlated them to the three‐dimensional structure of buried basement faults. Our results reveal an unprecedented detail of the basement fabric dominated by high‐frequency WNW to NW trending magnetic lineaments associated with the Precambrian Mughese Shear Zone fabric. The high‐frequency magnetic lineaments are superimposed by lower frequency NNW trending magnetic lineaments associated with possible Cenozoic faults. Surface ruptures associated with the 2009 Mw 6.0 Karonga earthquake swarm aligned with one of the NNW‐trending magnetic lineaments defining a normal fault that is characterized by right‐stepping segments along its northern half and coalesced segments on its southern half. Fault geometries, regional kinematics, and spatial distribution of seismicity suggest that seismogenic faults reactivated the basement fabric found along the half‐graben hinge zone. We suggest that focusing of strain accommodation and seismicity along the half‐graben hinge zone is facilitated and modulated by the presence of the basement fabric.

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Spectral P-wave magnitudes, magnitude spectra and other source parameters for the 1990 southern Sudan and the 2005 Lake Tanganyika earthquakes

Cited by 5 publications

References 27 publications

A semi-automated algorithm to quantify scarp morphology (SPARTA): application to normal faults in southern Malawi

A semi-automated algorithm to quantify scarp morphology (SPARTA): application to normal faults in southern Malawi

Active deformation of Malawi Rift’s North Basin hinge zone modulated by reactivation of pre-existing Precambrian shear zone fabric

Active Deformation of Malawi Rift's North Basin Hinge Zone Modulated by Reactivation of Preexisting Precambrian Shear Zone Fabric

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