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High-resolution record of displacement accumulation on an active normal fault: implications for models of slip accumulation during repeated earthquakes

High-resolution record of displacement accumulation on an active normal fault: implications for models of slip accumulation during repeated earthquakes
High-resolution record of displacement accumulation on an active normal fault: implications for models of slip accumulation during repeated earthquakes
The spatial and temporal accumulation of slip from multiple earthquake cycles on active faults is poorly understood. Here, we describe a methodology that can determine the time period of observation necessary to reliably constrain fault behaviour, using a high-resolution long-time-scale (the last 17kyr) fault displacement dataset over the Rangitaiki Fault (Whakatane Graben, New Zealand). The fault linked at c. 300 ka BP, and analysis of time periods within the last 17 kyr gives insight into steady-state behaviour for time intervals as short as c. 2 kyr. The maximum displacement rate observed on the Rangitaiki Fault is 3.6 ± 1.1 mm yr-1 measured over 17 kyr. Displacement profiles of the last 9 ka of fault movement are similar to profiles showing the last 300 ka of fault movement. In contrast, profiles determined for short time intervals (2 - 3 kyr) are highly irregular and show points of zero displacement on the larger segments. This indicates temporal and spatial variability in incremental displacement associated with surface-rupturing slip events. There is spatial variability in slip rates along fault segments, with minima at locations of fault interaction or where fault linkage has occurred in the past. This evidence suggests that some earthquakes appear to have been confined to specific segments, whereas larger composite ruptures have involved the entire fault. The short-term variability in fault behaviour suggests that fault activity rates inferred from geodetic surveys or surface ruptures from a single earthquake, may not adequately represent the longer-term activity nor reflect its future behaviour. Different magnitude events may occur along the same fault segment, with asperities preventing whole segment rupture for smaller magnitude events.
earthquake recurrence intervals, fault displacement rates, fault linkage, mormal faulting
0191-8141
1146-1166
Bull, J.M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Barnes, P.M.
83833300-fb73-4774-b563-65dfd8e22ca9
Lamarche, G.
79c06f89-5fdb-40dc-bd37-eb4e69ee8fb0
Sanderson, D.J.
5653bc11-b905-4985-8c16-c655b2170ba9
Cowie, P.A.
3ba1c8f4-680d-42e5-b944-1a8954666ba9
Taylor, S.K.
6d3a9f25-19f2-469d-9bc0-782c5865c366
Dix, J.K.
efbb0b6e-7dfd-47e1-ae96-92412bd45628
Bull, J.M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Barnes, P.M.
83833300-fb73-4774-b563-65dfd8e22ca9
Lamarche, G.
79c06f89-5fdb-40dc-bd37-eb4e69ee8fb0
Sanderson, D.J.
5653bc11-b905-4985-8c16-c655b2170ba9
Cowie, P.A.
3ba1c8f4-680d-42e5-b944-1a8954666ba9
Taylor, S.K.
6d3a9f25-19f2-469d-9bc0-782c5865c366
Dix, J.K.
efbb0b6e-7dfd-47e1-ae96-92412bd45628

Bull, J.M., Barnes, P.M., Lamarche, G., Sanderson, D.J., Cowie, P.A., Taylor, S.K. and Dix, J.K. (2006) High-resolution record of displacement accumulation on an active normal fault: implications for models of slip accumulation during repeated earthquakes. Journal of Structural Geology, 28 (7), 1146-1166. (doi:10.1016/j.jsg.2006.03.006).

Record type: Article

Abstract

The spatial and temporal accumulation of slip from multiple earthquake cycles on active faults is poorly understood. Here, we describe a methodology that can determine the time period of observation necessary to reliably constrain fault behaviour, using a high-resolution long-time-scale (the last 17kyr) fault displacement dataset over the Rangitaiki Fault (Whakatane Graben, New Zealand). The fault linked at c. 300 ka BP, and analysis of time periods within the last 17 kyr gives insight into steady-state behaviour for time intervals as short as c. 2 kyr. The maximum displacement rate observed on the Rangitaiki Fault is 3.6 ± 1.1 mm yr-1 measured over 17 kyr. Displacement profiles of the last 9 ka of fault movement are similar to profiles showing the last 300 ka of fault movement. In contrast, profiles determined for short time intervals (2 - 3 kyr) are highly irregular and show points of zero displacement on the larger segments. This indicates temporal and spatial variability in incremental displacement associated with surface-rupturing slip events. There is spatial variability in slip rates along fault segments, with minima at locations of fault interaction or where fault linkage has occurred in the past. This evidence suggests that some earthquakes appear to have been confined to specific segments, whereas larger composite ruptures have involved the entire fault. The short-term variability in fault behaviour suggests that fault activity rates inferred from geodetic surveys or surface ruptures from a single earthquake, may not adequately represent the longer-term activity nor reflect its future behaviour. Different magnitude events may occur along the same fault segment, with asperities preventing whole segment rupture for smaller magnitude events.

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Published date: July 2006
Keywords: earthquake recurrence intervals, fault displacement rates, fault linkage, mormal faulting

Identifiers

Local EPrints ID: 40816
URI: http://eprints.soton.ac.uk/id/eprint/40816
ISSN: 0191-8141
PURE UUID: 3696b432-fac5-4a0c-938a-eb9e7d81edfe
ORCID for D.J. Sanderson: ORCID iD orcid.org/0000-0002-2144-3527

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Date deposited: 10 Jul 2006
Last modified: 17 Dec 2019 01:43

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