X Close

UCL IRDR Blog

Home

UCL Institute for Risk and Disaster Reduction

Menu

Using Fault data in seismic hazard and risk assessment: A fault2SHA initiative

Joanna P Faure Walker22 March 2021

Effective fault data presentation helps make progress in the calculation of earthquake hazard and risk. 

Cross-disciplinary working can help progress. For calculating seismic hazard, the Fault2SHA Working Group has brought together data providers, modellers and seismic hazard and risk practitioners to help promote the use of fault data in seismic hazard assessment… Fault2SHA representing fault – to – seismic hazard assessment.

In the case of earthquake hazard and risk calculations, a key barrier to fault-based seismic hazard assessment has been the availability of data in a format that can be easily incorporated into calculations of hazard and risk. This has hindered efforts to provide long-term views of hazard and risk. Long-term, multi-millennia time frames cover several seismic cycles such that the long-term behaviour of faults can be identified and not miss out faults capable of hosting earthquakes which have not ruptured within a short-term observation periods (tens or hundreds of years). A further restriction has been the difficulty for modellers to interrogate the detail and uncertainties in primary data. To address these issues, the Fault2SHA Central Apennines laboratory, led by Dr Joanna Faure Walker (UCL IRDR), has created a database structure demonstrating a usable format by which geologists can present data that can be directly incorporated into hazard and risk calculations. To demonstrate its effectiveness, the laboratory has tested the database to calculate simplified calculations of risk in the Central Apennines and demonstrated the effectiveness, even at a simple level, for identifying which faults threaten the public the most and where additional data would have the most impact on current calculations. It is hoped those working in other regions can help the endeavour of promoting the use of faults in seismic hazard assessment through adopting a similar approach.

This work brings together researchers from different research groups in the UK, Italy and France: Joanna Faure Walker, Paolo Boncio, Bruno Pace, Gerald Roberts, Lucilla Benedetti, Oona Scotti, Francesco Visini, and Laura Peruzza

The two papers are published Scientific Data and Frontiers in Earth Science, while the database is available through PANGAEA.

Fault2SHA Central Apennines Database and structuring active fault data for seismic hazard assessment 

Which Fault Threatens Me Most? Bridging the Gap Between Geologic Data-Providers and Seismic Risk Practitioners

Fault2SHA Central Apennines Database

The Fault2SHA working group runs a monthly online learning series to help cross-disciplinary working and annual workshops.  The learning series and 2020 workshop is available through the Fault2SHA youtube channel. A summary of the database is provided by Joanna at 17 mins into the first session of the Fault2SHA 5th workshop:Promoting Faults in Seismic Hazard Assessment

 

Study of Icelandic active faults shows fault bends must be considered throughout fault development and maturity

Joanna P Faure Walker9 July 2020

Iezzi, Roberts & Faure Walker (2020) Throw-rate variations within linkage zones during the growth of normal faults: Case studies from the Western Volcanic Zone, Iceland, J. Struct. Geol., 133, 103977

Fault throw-rates and slip-rates are a fundamental input into fault-based seismic hazard assessments (SHA) i.e. how likely are earthquakes to occur….

Francesco Iezzi, Gerald Roberts and Joanna Faure Walker studied active faults in the Western Volcanic Zone, Iceland, to determine whether changes in fault throw-rates across fault bends, as identified in previous works in central Italy, are present in other tectonic settings.

This study shows that fault throw-rate increases within fault bends in response to non-planar fault geometry are present at a range of stages of maturity of the bend and extends examples of this phenomenon to mid-ocean ridge settings. This suggests that extrapolating fault slip-rates and slip during past earthquakes from individual sites along a fault must consider the location of data collection in relation to the geometry of the fault.

Why is this so important? Because if we use individual measurements of how fast a fault is moving, we need to understand whether this measurement is representative of the fault as a whole or whether it is underestimating or overestimating the slip. If we do not do this, we will overestimate or underestimate earthquake hazard.

A step closer in earthquake forecasting

Joanna P Faure Walker16 August 2019

Dr Zoe Mildon, former IRDR PhD student and now lecturer at University of Plymouth, together with Dr Joanna Faure Walker  (UCL IRDR), Prof Gerald Roberts (Birkbeck) and Prof Shinji Toda (Tohoku University IRIDeS), have published a paper in Nature Communications showing we are a step closer in understanding which faults could rupture in the next earthquake:

Coulomb pre-stress and fault bends are ignored yet vital factors for earthquake triggering and hazard

In this paper, we use long-term stress loading on faults in the central Apennines, Italy, together with stress loading from historical earthquakes in the region to test whether we can identify faults which have a positive stress and hence are ripe for rupture.  We found that 97% large earthquakes within the central Italian Apennines from 1703-2006 occurred on positively stressed faults. Therefore, we can use our modelling to calculate which faults are currently positively stressed and hence help us to determine which faults could rupture in the future. This is not the same as earthquake prediction – saying exactly when and where an earthquake will occur, but it is a step closer to better seismic hazard assessments and understanding why, how and when earthquakes occur.

Dr Joanna Faure Walker standing by a limestone fault scarp in the central Italian Apennines

The paper is available through open access: Mildon et al. (2019)

An article was written about the paper in the Daily Mail

The original press release is available here.

This work is part of the IRDR’s continuing collaboration with Tohoku University, IRIDeS (International Research Institute for Disaster Science). Our collaboration has led to papers including topics such as earthquake stress transfer (Mildon et al., 2016), disaster fatalities (Suppasri et al., 2016), and temporary housing (e.g. Naylor et al., 2018).

New paper on segmented normal fault systems

Joanna P Faure Walker19 June 2019

Publication of: Occurrence of partial and total coseismic ruptures of segmented normal fault systems: Insights from the Central Apennines, Italy by Iezzi et al. (2019)

Francesco Iezzi (PhD student, Birkbeck) together with Prof Gerald Roberts (Birkbeck), Dr Joanna Faure Walker (IRDR) and Ioannis Papanikolaou (Agricultural University of Athens) have published a detailed study of the long-term displacements across the fault responsible for the 2009 L’Aquila Earthquake, Italy, and the surrounding faults. This reveals that the different faults are behaving together so that the displacement across the system of faults looks similar to if it were one larger fault on ten thousand and million year timescales. This finding can help provide clues regarding the relative local seismic hazard between the different fault segments. The study also provides evidence that the vertical displacement (throw) across a fault increases across fault bends, a result that has been demonstrated in previous papers by the research group (e.g. Faure Walker et al., 2009; Wilkinson et al., 2015, Iezzi et al., 2018). The Iezzi et al. (2019) paper discusses the synchronised and geometrically controlled activity rates on the studied faults in terms of the propensity for floating earthquakes, multi-fault earthquakes, and seismic hazard.

 

Photograph of damage following the 2009 L’Aquila earthquake, taken by Joanna Faure Walker while accompanying the EEFIT mission.

Fault responsible for 1908 Messina Earthquake found

Joanna P Faure Walker9 May 2019

In 1908 a Mw7.1 earthquake struck the town of Messina in Sicily, Italy.  This earthquake killed over 80,000 people making it the most deadly earthquake in Europe since 1900. Despite causing great losses and prompting research into earthquake environmental effects worldwide, the fault responsible for this earthquake has before now remained a source of contention.

However, new research has identified the fault responsible for this event. This was done using elastic half-space modelling and levelling data from 1907–1909. This research has highlighted the importance of studying mapped faults to locate past events.

This work was led by PhD student Marco Meschis (Birkbeck College) in collaboration with researchers from UCL IRDR, Birkbeck College, University of Plymouth and Università degli Studi dell’Insubria.

Meschis, Roberts, Mildon, Robertson, Michetti and Faure Walker (2019) Slip on a mapped normal fault for the 28thDecember 1908 Messina earthquake (Mw 7.1) in Italy, Scientific Reports, doi:10.1038/s41598-019-42915-2

Recent IRDR research on Italian earthquakes includes:

Iezzi,  Mildon, Faure Walker, Roberts, Wilkinson, Robertson, (2018) Coseismic Throw Variation Across Along-Strike Bends on Active Normal Faults: Implications for Displacement Versus Length Scaling of Earthquake Ruptures, Journal of Geophysical Research: Solid Earth 

Faure Walker J.P., 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), BSSA 109 (1), 110-123

 

Earthquake surface measurements reveal new revelations about how faults rupture

Joanna P Faure Walker12 November 2018

PhD student Francesco Iezzi (Birkbeck College), supervised by Prof Gerald Roberts (Birkbeck College) and Dr Joanna Faure Walker (UCL IRDR), has published a paper that could revolutionalise how geologists and seismic hazard modellers use long established scaling relationships between fault lengths and surface rupture parameters.

The paper is freely available to all and can be found here.

What new observations have been made?

For five earthquakes studied, the surface fault slip (the amount the fault surface moved during the earthquake) and the throw (the vertical component of the slip) was higher where there was a bend along the length of the fault.

Following the central Italy August and October 2017 earthquakes that ruptured the ground surface, we made detailed high spatial resolution measurements of surface fault displacement along the length of the surface fault ruptures. A study of the amount of vertical and horizontal displacement that occurred along the length of the fault revealed that the throw and slip that occurred during the earthquakes increased where there are bends in the fault. This result is critical and has not been identified before for individual earthquakes.

Damage in Amatrice from the August 2016 Earthquake. Photograph take during EEFIT fieldwork by Dr Joanna Faure Walker.

Why does this occur?

We hypothesis that this occurs in order to maintain the horizontal strain (change in length relative to the original length) across a fault during an earthquake and the long-term horizontal strain-rate that accumulates from multiple earthquakes over thousands of years.

Are there other examples of this?

We then went back and studied other examples earthquakes where there was enough information to determine whether a similar pattern of higher throw and slip could be seen across bends in the fault. In the three further events studied in USA Basin and Range, Greece, and Mexico, we found the same relationship. So it seems this phenomenon occurs worldwide in normal (extensional) faults.

This was the first time that the change in vertical component of slip during an earthquake has been shown to be predictable. However, the observed relationship of increased throw across fault bends has been identified previously in long-term displacements that have accumulated over 15 thousand years as a result of multiple earthquakes in Italy (Faure Walker et al., 2009, Wilkinson et al., 2015). Before now, it was not known whether this increase was caused by there being more earthquakes across the bends or more movement during individual events.  We now know that there can be more slip during individual events, however we do not know whether this is the only mechanism for creating a long-term higher throw-rate across the bends.

What does this mean for earthquake science?

This paper suggests that slip during an earthquake will change where there is a bend along the length of the fault and this change can be quantified and predicted using the proposed theory. This means that close to the fault, earthquakes may be more damaging near a bend in the fault. This finding suggests that we cannot use fault scaling relationships between fault length and expected slip in earthquakes without consideration of fault geometry. This paper can also explain much of the scatter seen in existing plots of maximum surface slip against fault length because when collecting the data as input for such relationships, consideration was not given about whether the measurements were taken across fault bends or not.

These changes in slip along faults in individual earthquakes related to the fault geometry should be included in probabilistic seismic hazard assessments (PSHA).

What other research in the IRDR relates to this?

This work contributes to the IRDR and colleagues’ work on investigating fault behaviour to improve our understanding of earthquake hazard. Recent papers have demonstrated the importance of including detailed fault geometry and slip-rates in seismic hazard calculations (Faure Walker et al., 2018) and Coulomb stress transfer calculations (Mildon et al., 2016, 2017).

Iezzi et al (2018), Coseismic Throw Variation Across Along‐Strike Bends on Active Normal Faults: Implications for Displacement Versus Length Scaling of Earthquake Ruptures, Journal of Geophysical Research, https://doi.org/10.1029/2018JB016732 

More data needed for better earthquake hazard and risk calculations

Joanna P Faure 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.

Induced earthquakes – how and when they have occurred, and why should anyone care

Joanna P Faure Walker27 September 2018

Despite the high volume of material out there about induced earthquakes, it can be hard to separate fact from opinion. To help explain what induced seismicity is, how it is caused and what the risks are, a group of researchers from UCL Department of Chemical Engineering and Institute for Risk and Disaster Reduction have published “Addressing the risks of induced seismicity in subsurface energy operations”.

What causes “induced seismicity”? Induced earthquakes, those mainly caused by human action, can invoke strong feelings towards the processes that cause them, the most widely known among these is hydraulic fracturing (less favourably known as “fracking”). But hydraulic fracturing for shale gas extraction is not the only cause of induced earthquakes – several industrial activities are capable of inducing or triggering earthquakes, including mining, dams, conventional oil and gas operations, groundwater extraction, CO2 Capture and Storage (CCS), underground waste fluid disposal and the creation of geothermal energy systems. Rightly or wrongly, negative public perception and local public opposition to induced seismicity has led to numerous international projections having been suspended, delayed or curtailed.

How does industrial operation induce earthquakes? The Earth’s crust is believed to be in a state where it is critically stressed and only small stress changes in the right direction can cause an earthquake. Industrial action can alter the stress field in the most shallow part of the Earth’s crust, inducing a seismic event.

Are these events getting more likely? The number of documented cases of man-made earthquakes in different industrial activities is rapidly increasing: In 2017 alone, there were two reported record-breaking magnitude induced seismic events. One of the more well-known areas of induced seismicity is in the United States: The notable increase in seismicity within the last decade in the previously seismically quiet State of Oklahoma has been widely attributed to large scale waste water injection wells connected to the hydrocarbon production industry.

How big are induced earthquakes? Most induced earthquakes are low in magnitude (typically less than magnitude 4). However, even these small events are capable of causing structural damage to properties and evoking widespread fear and anxiety. We say most are small, but there are some examples where large magnitude earthquakes have been alleged to be caused by human activities. For example, in China in 2008, a dam was built that filled a reservoir behind it. A short time later, a magnitude 8 earthquake occurred in the region. Some scientists proposed this large earthquake was caused by the mass loading of the water in the dam and its penetration into rock, affecting the subsurface pressure in an underlying fault line and possibly setting off a series of ruptures that led to the earthquake.

So what is being done about it? Minimising seismic risk should be a high priority for industrial operators. All fluid injection processes should require detailed seismic hazard assessments for imaging and characterising faults prior to operations, with dedicated monitoring systems in addition to existing national seismic monitoring facilities. For assessing the risks, monitoring the operations, and designing mitigation strategies using predictive models that can characterise the spatiotemporal evolution of induced seismicity would be extremely helpful. Examples of best practice approaches show that maintaining a transparent dialogue between operator and the public, while adhering to the regulatory processes can allow safe operations in an atmosphere of public acceptance.

Where can I find out more? With all the controversy around such events, we need to understand what are the risks of induced earthquakes and how can we model them. In the published article in Wiley Interdisciplinary Reviews, Richard Porter, Alberto Atriolo, Haroun Mahgerefteh and Joanna Faure Walker provide a review of several alleged induced seismicity case studies that have occurred in the last 15 years covering a variety of causal mechanisms. We discuss issues relating to public perception and procedures and strategies that could be implemented to help prevent and mitigate future occurrences.

The above work was funded by Horizon 2020 research and innovation programme, Grant/Award Number: 640979

Fault2SHA has successful session at ESC 2018 in Malta

Joanna P Faure Walker7 September 2018

The Fault2SHA ESC (European Seismological Commission) Working Group hosted a session on Wednesday 5th September at the ESC 2018 Meeting held in Valletta, Malta. Oona Scotti represented the group in her keynote on the opening day of the conference, in which she addressed “Modelling fault systems in PSHA: Challenges Ahead”. The Fault2SHA Working Group, for which I am on the Executive Committee, links different researchers working on faults and seismic hazard assessment (SHA) in Europe and beyond. This collaboration has brought together field geologists, fault-modellers and probabilistic seismic hazard modellers. The group provides a forum in which data, results, modelling capabilities, and improvements in scientific understanding can be shared. If you want more information, and to join, see Fault2SHA. The next Fault2SHA workshop will be in Kaust, Saudi Arabia, in November 2018 and the next meeting will run on 3rd-5th June 2019 in Barcelona, Spain.

I lead the Fault2SHA Central Apennines Laboratory. Our team comprises researchers from Italy (Paolo Boncio, Bruno Pace, Laura Peruzza, Francesco Visini), France (Lucilla Benedetti, Ooona Scotti) and the UK (Joanna Faure Walker, Gerald Roberts). At ESC in Malta, I introduced the central Apennines Laboratory and our current activities to the wider working group. The Central Apennines, as well as being a beautiful place to conduct fieldwork with the opportunity to obtain detailed datasets, suffers from large magnitude earthquakes. Indeed, earthquakes in the Central Apennines have featured widely in the UK press due hosting the two deadliest earthquakes in Europe of the last ten years: the 2009 L’Aquila sequence and the 2016 Amatrice-Norcia sequence.

 

The Fault2SHA Central Apennines Laboratory, which formed in January 2018, held an in-person meeting in July at the University of Chieti-Pescara, Italy. The photograph shows (from left to right) Oona Scotti, Francesco Visini, Joanna Faure Walker, Bruno Pace, Laura Peruzzi, Lucilla Benedetti, and Paolo Boncio.

During the Fault2SHA ESC session, I presented a second talk and a poster about my research investigating the importance of incorporating detailed fault geometry for understanding seismic hazard. The oral presentation demonstrated the importance of incorporating detailed fault geometry and loading on faults between earthquakes in Coulomb Stress Transfer modelling, a process that causes the stress on faults to change in response to an earthquake on a neighbouring fault. This was based on work carried out by Zoe Mildon (former IRDR PhD student, now a lecturer at the University of Plymouth) in collaboration with Gerald Roberts, Shinji Toda and myself (see Midon et al. 2016 and Mildon et al. submitted preprint). The poster displayed the importance of detailed fault geometry and slip-rate data for calculating earthquake probabilities and ground shaking intensities. I further represented Zoe for her poster within the session on earthquakes in regions of distributed deformation, that showed surface ruptures from the 1997 Colfiorito Earthquake in the central Apennines was due to primary earthquake slip (see Mildon et al., 2016 for details).

I thank all those at the conference with whom I had interesting discussions and I look forward to seeing all of our research progress.

IRDR Masters student publishes Early Warning and Temporary Housing Research. This is part of the on-going collaboration between UCL-IRDR and IRIDeS-Tohoku University

Joanna P Faure Walker4 June 2018

Angus Naylor, an IRDR Masters student alumni and Masters Prize Winner, has published the research conducted for his Independent Research Project. The research was carried out as part of his MSc Risk, Disaster and Resilience with me, his project supervisor, and our collaborator at Tohoku University IRIDeS (International Research Institute of Disaster Science), Dr Anawat Suppasri.

Following the Great East Japan Earthquake and Tsunami in 2011, UCL-IRDR and Tohoku University IRIDeS wanted to join forces to learn more about both the fundamental science and impacts of disasters both in Japan and around the world. Naylor’s recently published paper adds to other collaborative outputs from the two institutes: Mildon et al., 2016, investigating Coulomb Stress Transfer within the area of earthquake hazard research; Suppasri et al., 2016 investigating fatality ratios following the 2011 Great East Japan Tsunami; and IRDR Special Report 2014-01 on the destruction from Typhoon Yolanda in the Philippines. The two institutions have met on a number of occasions, and have an upcoming symposium in October 2018.

In 2014, three and half years after the Great East Japan Earthquake and Tsunami destroyed much of Tohoku’s coastline, I led and Dr Anawat Suppasri organised a joint UCL-IRDR and Tohoku University IRIDeS team, visiting residents of six temporary housing complexes in Miyagi and Iwate prefectures. While there, we used written questionnaires and informal group interviews to investigate the suitability of early warning systems and the temporary housing among the elderly population affected by this event.

When analysing the results, we found overall that age was not the principal factor in affecting whether a warning was received, but did play a significant role regarding what was known before the warning was received, whether action was taken and how temporary and permanent housing was viewed. The results suggest that although the majority of respondents received some form of warning (81%), no one method of warning reached more than 45% of them, demonstrating the need for multiple forms of early warning system alerts. Furthermore, only half the respondents had prior knowledge of evacuation plans with few attending evacuation drills and there was a general lack of knowledge regarding shelter plans following a disaster. Regarding shelter, it seems that the “lessons learned” from the 1995 Kobe Earthquake were perhaps not so learnt, but rather many of the concerns raised among the elderly in temporary housing echoed the complaints from 16 years earlier: solitary living, too small, not enough heating or sound insulation and a lack of privacy.

An example of Temporary Housing following the Great East Japan Earthquake and Tsunami visited during the fieldwork for this study (Photograph: Dr Joanna Faure Walker)

The research supports previous assertions that disasters can increase the relative vulnerabilities of those already amongst the most vulnerable in society. This highlights that in order to increase resilience against future disasters, we need to consider the elderly and other vulnerable groups within the entire Early Warning System process from education to evacuation and for temporary housing in the transitional phase of recovery.

The paper, ‘Suitability of the early warning systems and temporary housing for the elderly population in the immediacy and transitional recovery phase of the 2011 Great East Japan Earthquake and Tsunami’ published in the International Journal of Disaster Risk Reduction, can be accessed for free until 26th July here, after this date please click here for standard access.

The authors are grateful for the fieldwork funds which came from The Great British Sasakawa Foundation funding to UCL-IRDR and MEXT’s funding to IRIDeS. The joint UCL-IRDR1 and IRIDeS2 fieldwork team comprised Joanna Faure Walker1, Anawat Suppasri2, David Alexander1, Sebastian Penmellen Boret2, Peter Sammonds1, Rosanna Smith1, and Carine Yi2.

Angus Naylor is currently doing a PhD at Leeds University
Dr Joanna Faure Walker is a Senior Lecturer at UCL IRDR
Dr Anawat Suppasri is an Associate Professor at IRIDeS-Tohoku University