Download Micro-morphology of normal fault scarps

IAPETUS
doctoral training partnership
Micro-morphology of normal fault scarps
Project reference IAP/14/50. Please quote this reference when applying.
Durham University, Dept of Earth Sciences
In partnership with University of Glasgow, Dept of Geographical & Earth
Sciences
Supervisory Team
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Key Words
Active faults, Normal Faults, LiDAR, geomorphology, slip rate
Prof Ken McCaffrey, Durham University
Dr Seamus Coveney, Glasgow University
Prof Gerald Roberts, Birkbeck, U. of London
Dr Nicola De Paola, Durham University
Overview
Active normal faults produce surface offsets and scarp
at the Earth’s surface through the mechanism of fault
slip during earthquakes1. Fault scarps in the central
Italian Apennines (Abbruzzo) exhibit striated fault
planes, offset dated Holocene sediments and
geomorphic surfaces, and are the surface expression
of a network of active normal faults formed over the
past 2-3 Myrs.
Preliminary results have shown that scarp morphology
may be correlated with fault slip rate and the aim for
this study will be to fully explore this relationship.
Terrestrial and Airborne Laser Scan (TLS & ALS)
datasets provide a new approach to mapping the
geomorphology of active normal faults3. TLS datasets
provide an accurate digital representation of the real
world topography.
The student will use TLS and ALS datasets to quantify
slip rates for faults in the central Appenines High
resolution TLS scans of the scarps will enable him/her
to quantify the mm to cm scale morphology on the
fault scarps. The results will feed into our knowledge
of the slip rate patterns and variations on Italian faults.
The work in general impacts seismic hazard
assessment in Italy because earthquake recurrence
intervals reflect long and short term throw rates. In
addition, the geomorphic expression of fault segments
depends on slip rate and hence controls sediment
input into basins and resulting stratigraphic patterns.
Methodology
Preservation of scarps depends on the interplay
between fault slip rate (throw rate) and geomorphic
processes that are able to alter surface offset and the
scarp exposures. Recent studies have shown that fault
slip rates can vary significantly from geodeticallydetermined regional extensional rates both in time
and space depending on fault geometry2, and the
ability to interact with neighbouring structures.
Building on previous studies that have established a
methodology and produced intial results, the student
will perform a geomorphic analysis of TLS & ALS
datasets from the central Apennines in Italy. The data
take the form of a point cloud that includes all returns
from the laser scan survey. These point clouds will be
processed to remove all points which are not ground
returns using established filtering and manual editing
routines. The geometric relationship between these
points in 3D space will also be determined to provide
additional
information
to
aid
geomorphic
interpretation. The ground return points will then be
meshed to form a Triangulated irregular network
(TIN) and displayed as a bare earth hillshade rasters.
A geomorphic interpretation will then be made to
study the effects of erosional, depositional processes
on the preserved scarps using a combination of
manual and semi-automated methods. Slip rates can
be determined using semi-automatic cross-sectional
tools and maps compiled to show spatial variations.
Subtle changes in slope can be used to identify
important geomorphic features4. Such features include
bowl-shaped rotational slips, colluvial wedges, alluvial
fan deposits as well as footwall bedrock gullies and
hangingwall erosional channels. Thus, reliable long
term 105 yr slip rate determinations will be made at
the best preserved portions of scarps along the entire
traces of the normal faults.
Roughness parameters will be calculated for point
cloud strips scarps aligned along the slip direction for
individual faults. For a number of the faults in the
study area, these morphology parameters will be
correlated with short term slip rates (<103 yrs) based
on modelled results from 36Cl cosmogenic dating
being generated in related NERC-funded research by
the supervisors.
of use to other geoscientists working in active
tectonic fields and earthquake science.
The results will be used to make an assessment of the
feasibility of using morphology measures as a proxy
for slip rate. The work will also provide new insights
on scarp creation, preservation and degradation
processes in carbonate-hosted normal faults. Any
systematic natural variation of fault scarp morphology
with tectonic or geomorphological processes will be
Further Information
Timeline
Q1 Q2
Induction, training, lit review
Fieldwork
Data Analysis
Results interpretation
Paper preparation
Thesis chapter
writing
Q3
Q4
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
Q1
Q2
Training & Skills
 Geomatic methods including Terrestrial laser scan
Lidar) applications
 3D geospatial analysis of structures
 Geomorphology,
Earthquake
Science
and
Paleoseismology
References & Further Reading
[1] Roberts, G.P., Michetti, A.M., 2004. Spatial and temporal
variations in growth rates along active normal fault systems: an
example from the Lazio-Abruzzo Apennines, central Italy. Journal
of Structural Geology 26, 339–376.
[2] Faure Walker J., Roberts G.P., Cowie P.A., Papanikolaou I.,
Michetti A.M., Sammonds P. and Phillips R., Horizontal strain-rates
and throw-rates across breached relay-zones, central Italy:
implications for the preservation of throw deficits at points of
normal fault linkage, Journal of Structural Geology, 31, 386 11451160.
[3] Wilkinson et al. 2014. Slip rate analysis of the Campo Felice
fault from Terrestrial laser scan datasets. Geomorphology.
[4] Bubeck et al 2014. The tectonic geomorphology of bedrock
scarps on active normal faults in the Italian Apennines mapped
using combined ground penetrating radar and terrestrial laser
scanning. Geomorphology.
Email: Ken McCaffrey - [email protected]