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| Titel |
Millennial strain partitioning revealed by 36Cl cosmogenic data on active bedrock fault scarps from Abruzzo, Italy |
| VerfasserIn |
Laura Gregory, Gerald Roberts, Patience Cowie, Luke Wedmore, Ken McCaffrey, Richard Shanks, Leo Zijerveld, Richard Phillips |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145523
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| Publikation (Nr.) |
 EGU/EGU2017-9471.pdf |
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| Zusammenfassung |
| In zones of distributed continental faulting, it is critical to understand how slip is partitioned
onto brittle structures over both long-term millennial time scales and shorter-term individual
earthquake cycles. Measuring earthquake slip histories on different timescales is
challenging due to earthquake repeat-times being longer or similar to historical
earthquake records, and a paucity of data on fault activity covering millennial to
Quaternary scales in detail. Cosmogenic isotope analyses from bedrock fault scarps have
the potential to bridge the gap, as these datasets track the exposure of fault planes
due to earthquakes with millennial resolution. In this presentation, we present new
36Cl data combined with historical earthquake records to document orogen-wide
changes in the distribution of seismicity on millennial timescales in Abruzzo, central
Italy.
Seismic activity due to extensional faulting was concentrated on the northwest side of the
mountain range during the historical period, or since approximately the 14th century.
Seismicity is more limited on the southwest side of Abruzzo during historical times. This
pattern has led some to suggest that faults on the southwest side of Abruzzo are not active,
however clear fault scarps cutting Holocene-aged slopes are well preserved across the whole
of the orogen. These scarps preserve an excellent record of Late Pleistocene to
Holocene earthquake activity, which can be quantified using cosmogenic isotopes that
track the exposure of the bedrock fault scarps. 36Cl accumulates in the fault scarps
as the plane is progressively exhumed by earthquakes and the concentration of
36Cl measured up the fault plane reflects the rate and patterns of slip. We utilise
Bayesian modelling techniques to estimate slip histories based on the cosmogenic data.
Each sampling site is carefully characterised using LiDAR and GPR to ensure that
fault plane exposure is due to slip during earthquakes and not sediment transport
processes.
In this presentation we will focus on new data from faults located across-strike in
Abruzzo. Many faults in Abruzzo demonstrate slip rate variability on millennial timescales,
with relatively fast slip interspersed between quiescent periods. We show that heightened
activity is co-located and spatially migrates across Abruzzo over time. We highlight the
importance of understanding this dynamic fault behaviour of migrating seismic activity, and
in particular how our research is relevant to the 2016 Amatrice-Vettore seismic sequence in
central Italy. |
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