X Close

UCL IRDR Blog

Home

UCL Institute for Risk and Disaster Reduction

Menu

More data needed for better earthquake hazard and risk calculations

Joanna PFaure Walker6 November 2018

New research demonstrates the importance of having detailed measurements at multiple sites along a fault of how fast the fault is moving and how the surface orientation of the fault changes. To access the full paper click here.

Why do we need fault measurements?

Measurements of fault slip rate and the geometry of the fault (it’s 3d orientation) can be used to calculate earthquake recurrence intervals to give probabilities of how likely earthquakes of different magnitudes are to occur. We also need these measurements to model how much ground shaking there will be at given locations. Hazard maps of expected ground shaking can be used to inform building codes and identify where buildings including homes and schools might need retrofitting to improve their resistance to earthquake shaking.

There are other methods available for creating earthquake hazard maps, such as using historical records of earthquake shaking. However, these records unlikely go back far enough in time to capture all faults capable of hosting large earthquakes because some faults will not have hosted earthquake within the time period covered by such records. Therefore, the hazard from some faults would be missing in hazard maps based solely on historical seismicity leading to underestimations in earthquake hazard.

What new insights have been revealed in the research publication?

The paper, entitled “Variable fault geometry suggests detailed fault slip rate profiles and geometries are needed for fault-based probabilistic seismic hazard assessment (PSHA)” demonstrates that relying on only one or a few measurements of how fast the fault is moving along a fault and projecting these measurements along the entire fault may lead to underestimating the uncertainty in the earthquake hazard calculations. Crucially, there may be locations where the hazard is underestimated, meaning people could be at more risk than suggested by simpler models (the converse is also possible). Therefore, earthquake hazard assessments based on fault parameters need to either use detailed measurements including measurements of how fast the fault is moving at multiple sites along the fault or to incorporate how the lack of such data increases the uncertainty in calculated earthquake hazard assessments.

Why are detailed measurements not being already used?

In many regions it is difficult to constrain the fault slip rate (how much the fault has moved in a given time) or throw rate (vertical component of slip rate) along a fault at even one location, let alone several. However, there are regions where this is possible so as more data is collected, this detail should help to improve earthquake hazard assessments both in those regions and worldwide.

Where can I find out more?

Faure Walker J., Visini F., Roberts G., Galasso C., McCaffrey K., and Mildon Z., (2018) Variable fault geometry suggests detailed fault slip rate profiles and geometries are needed for fault-based probabilistic seismic hazard assessment (PSHA), Bulletin of the Seismological Society of America, doi: 10.1785/0120180137

The Fault2SHA Working Group is an ESC (European Seismological Commission) group of researchers in both universities and civil protection authorities collaborating to increase incorporation of fault data in seismic hazard assessments and to improve our understanding of how such data should be used.

Roots of earthquake-prone faults brought to light

Joanna PFaure Walker25 November 2013

Earthquakes affect many highly populated areas around the world so understanding what controls the distribution and frequency of them is a top priority for the earth science and disaster risk reduction communities. Often, however, the controlling factors remain elusive because scientists have limited information about what happens deep down in the Earth’s crust where earthquakes initiate. A recent Nature Geoscience article (Cowie et al. (2013) published online on 3rd November, 2013) has shed light on the problem, and has shown how phenomena on the surface can be linked to the movement of rocks in the deep crust.

(more…)

Fieldwork in Abruzzo: Four years on from L’Aquila

LukeWedmore19 April 2013

With the 4-year anniversary of the devastating L’Aquila earthquake occurring in the middle of my first PhD fieldtrip to Italy, the importance of studying active faults in the Abruzzo region remained at the front of my thoughts throughout my trip. The aim of the trip was to use Laser scanning (LiDAR) and ground penetrating radar (GPR) to increase our understanding of the active earthquake faults in the area. The group comprised Dr. Joanna Faure Walker (UCL IRDR), Dr. Ken McCaffrey (Durham University) and Dr. Laura Gregory (University of Leeds).

Dr. Ken McCaffrey (Durham University) using LiDAR to scan active normal faults in Abruzzo

Dr. Ken McCaffrey (Durham University) using LiDAR to scan active normal faults in Abruzzo

The first week was spent collecting GPR and LiDAR data along active faults, while the second week was spent hunting for potential future data collection sites. The active normal faults in this area can be seen in the landscape due to the existence of prominent limestone bedrock fault scarps on the side of steep mountains. However, such fault scarps are not present everywhere; for example, part of the fault responsible for the 1915 Avezzano earthquake that killed over 30,000 people crosses the Fucino plain. The Fucino basin is a former lake bed that was drained in the 1800’s. Consequently, the fault scarp has been obscured by erosion from the lake and more recently by intensive farming. LiDAR scans of sites along the fault trace within the plain ensure that we have a 3D digital image of the current state of the fault.

LiDAR scanning on the Fucino Plain

During the course of the two-week trip I visited 10 active faults across the region of Abruzzo and collected large quantities of data to process over the coming months. Visiting the faults for the first time was invaluable to my understanding of the earthquake hazard and overall seismic risk that people in the area are subject to.  Observing spectacular villages that cling to the sides of mountains located in the hanging walls of active faults and larger towns in the basins below highlighted the potentially devastating impact earthquakes in the area could have.  The results of my work will feed into a larger NERC funded study which aims to determine the time since each active fault last produced an earthquake; being a first year PhD student, this is a fantastic opportunity for me and I am looking forward to contributing to such an innovative and exciting project.