A 7.5 magnitude earthquake struck Noto Peninsula of Japan on New Year’s Day in 2024. Family members had come home to celebrate the New Year when the earthquake hit. Japan has a high level of awareness on disaster preparedness and mitigation. Despite this, more than 240 people lost their lives, 60,000 buildings were damaged and 25,000 people had to be evacuated from their homes. It is important to note that the deaths were caused by the earthquake where several buildings, especially the old structures collapsed. The new year’s earthquake also caused a tsunami, which arrived only a few minutes after the earthquake. However, the majority of people died from earthquakes, with only two people killed by the tsunami, which shows high awareness about tsunami preparedness among the general population, compared to the earthquakes. This shows more work needs to be done on earthquake preparedness in Japan, beyond a focus on developing and investing in resilient infrastructure.

In this short blog, we will shed some light on the experiences of people who are managing the evacuation centres, especially those evacuation centres that are led by the community. We will examine the current situation by putting gender and communities at the centre of our analysis.

Although there are many government run evacuation centres, there are also several community-run evacuation centres. In Japan, community-led shelters are commonly referred to as “voluntary shelters.” Leaders of these shelters typically include local community figures and temple and shrine heads, and, as observed during the Great East Japan Earthquake, leaders of traditional performing arts groups have frequently assumed these roles. Importantly, the foremost consideration for these community-oriented shelters is their trustworthiness. What we found was that due to the gender division of labour, which is still strongly present in Japanese society, taking care of the people in the evacuation centres becomes and remains the responsibility of women, including cooking, cleaning, and caretaking roles.

One important thing to note here is that these women, often wives/daughters/daughters-in-law, of the community leaders who automatically become the caretaker of the entire community in the times of crisis, are themselves the survivors of such events. However, they need to sacrifice their own needs and look after others. With harmony being the central key in Japanese social organisation, speaking of their own needs is seen as being selfish. Hence, no one is willing to do that: they would rather suffer than to bear the consequences of social stigma. This creates an environment where these women who are responsible for running the evacuation are often double victims: victims of the disaster and also the victims of post-disaster responsibilities.  

The person responsible for one of the evacuation centres we visited said it is comparatively manageable soon after the disaster as we only need to manage their immediate needs and there are more volunteers. However, as the time passes, people would like their normal life to return, which means a need for proper meals, proper sanitation, healthcare services, better accommodation and so on. The volunteers often go back to everyday life and the support from the government often dries out in about three months but the needs of those who are left behind – still in evacuation centres for various reasons – remain or they need even further support. Hence, taking care of the evacuees becomes a bigger responsibility, which needs to be factored into the discussions around disaster mitigation.

As evidenced during fieldwork and engagement activities in the communities affected by the earthquake in Noto, there are key local contexts and practices which must be appreciated and factored into future preparedness and response activities for disaster risk reduction. Discussions with stakeholders and local leaders for example highlighted the central value of community involvement in shaping and informing responses to disasters.

While it was reported that affected communities following the earthquake were more reserved in their engagement with the national government, they engaged readily and openly when responses were designed and driven by local communities, as evidenced by the creation of these community evacuation centres. These observations on the need to centre community involvement in disaster risk reduction and response are further substantiated by existing evidence from another disaster case study in Japan— the 2011 Tōhoku earthquake and tsunami which underscored a similar significance regarding the importance of contextually-appropriate and community-supported activities for disaster risk reduction and preparedness and response to events including earthquakes and tsunamis in regionally and geographically diverse countries, like Japan.

Our visit to the Noto Peninsula also revealed important observations and considerations on local understandings of leadership in disaster contexts, and how entrenched and gendered understandings of what constitute leadership can serve as a barrier to further vital involvement and participation of communities during events like earthquakes.  This was made apparent during discussions with female local leaders in Noto who had noted and reflected on how, despite their extensive involvement in disaster response and support activities, they did not consider themselves to be ‘leaders’ in these disaster contexts. Instead, many of their channels of leadership and support, including organising community efforts, food provision and emotional support had been regarded as traditionally ‘female’ associated practices and expectations rather than leadership roles during emergencies like earthquakes.

Again, this underscores the need to integrate local thinking and contexts in working to improve and promote local leadership during disasters in Japan by including gender frameworks to uncover how existing power dynamics and divisions of labour produce inequitable understandings of leadership, and where possible and when contextually-appropriate, to engage and work with these local communities to promote and centre diverse profiles and practices of disaster leadership and engagement of women and gender-diverse communities.

Our observations from these fieldwork activities investigating gender and women’s leadership in the Noto Peninsula also hold broader importance for the fields of disaster risk reduction and global health beyond preparing for and responding to earthquakes. Japan continues to be vulnerable to a broad scope of public health risks including earthquakes, tsunamis, volcanic activity, floods, typhoons and the climate change emergency. Despite ongoing disaster and resilience planning, there remains a critical need for the ongoing consideration and integration of gender-focused and community-centred participation and leadership activities as revealed during these fieldwork engagements to ensure that future responses and recovery to these events are both sustainable and equitable. 

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Co-authors

Dr Miwako Kitamura is an Assistant Professor at the International Research Institute of Disaster Science at Tohoku University

Dr Anawat Suppasri is an Associate Professor at the International Research Institute of Disaster Science at Tohoku University

Ms Hayley Leggett is a PhD candidate at the School of Engineering at Tohoku University

Dr Anna Matsukawa is an Associate Professor at University of Hyogo

Dr Stephen Roberts is Lecturer in Global Health at the Institute for Global Health at University College London

Dr Punam Yadav is an Associate Professor at the Institute for Risk and Disaster Reduction at University College London

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The views expressed in this blog are those of the author(s).

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Recognition of the different impacts of gendered norms is not new. We know that people are impacted differently in disasters and that attention needs to be paid to these differences while planning for preparedness, evacuation, response, and recovery. We also know that, like sexual and gender minorities, women are not a homogeneous group. However, have we paid enough attention to the impacts of culture-specific, often unspoken and implicit, gendered norms, which get exacerbated during crises? Often learnt through everyday practise, they are not only invisible to the outsiders but also to the insiders, taken for granted and seen as normal or obvious. The effects of such norms are often felt and experienced more by women and gender minorities than men. In this blog, we are going to talk about such unspoken norms in Japan and their impacts on people’s lives.

Wagamama

Here we would like to introduce a term, Wagamama. Interestingly many of us who live in the UK already know this term well, however, with a completely different understanding. ‘Wagamama’ is the name of a restaurant chain in the UK, which it says was inspired by fast-paced Japanese ramen bars. Many of us may have been there and enjoyed their delicious food. This restaurant portrays a positive meaning of this term of being self-indulgent, self-centred, picky, fussy, and so on. However, do we know the cultural meaning and interpretation of this term? How is it used and what does it really mean in Japanese culture?

Wagamama is a Japanese word, which means being selfish, demanding, or thinking about yourself and your own needs instead of others. This term is used to describe a certain behaviour of a person in a certain context. In some culture, it may be seen as a positive thing as the Wagamama restaurant portrays it to be. However, in Japan it is often used as a negative term. This term has a temporal element (which could have a long-term impact on people’s lives), as it is not a fixed characteristic of a person; however, it is used to describe a certain behaviour of a person.

Harmony

The opposite of this term is harmony. Harmony is key in Japanese culture and the meaning is quite vague leaving a lot of room for interpretation. Harmony generally means thinking about others and putting their needs before your own, which includes thinking not only about your family but the wider community too—and this becomes even more prevalent in the context of crisis. Although in theory this may look like a very good thing, having to live up to this expectation can create severe consequences for some. Non-compliance to maintaining ‘harmony’ means you are a Wagamama. This applies to all, including women, men, children, elderly, people with disability, and gender minority. However, for some people the consequences of non-compliance are severe. We will use some stories (based on real incidents) to illustrate this concept. However, we will use pseudonyms (and non-Japanese names) to avoid any indirect harm or unintended consequences.

Examples

Mike is a transgender man who was looking for a job. He went to the job centre to ask for help. He said as a transgender man he was facing difficulty in finding a job, so he needed help. Instead of helping him, the person at the job centre told him that it was selfish of him to expect that people should understand his gender identity—that he was thinking about himself and not others. Here one would think he hasn’t asked for anything, so why would anyone call him selfish? In a Japanese context, even disclosing your gender identity is seen as ‘Wagamama’—being selfish and not caring about other people. This becomes even more evident in the context of disaster as they are not meant to ask for any special treatment based on their gender identify, including any medical help.

People who worked in the evacuation centres during the 2011 Great East Japan Earthquake said it was very difficult to find out what women needed and what challenges they were facing as they would not speak for fear that if they asked for something—even for gender specific needs—people would call them Wagamama. Likewise, if food supplies were not adequate, then they will stay hungry and not announce that they have not eaten anything. Likewise, due to the gender division of roles and expectations, women were supposed to cook and feed everyone in the evacuation centres. Regardless of how tired they were or unwell they felt, they still had to carry on. They feared that if they said anything or asked for help, people will call them Wagamama.

These cultural expectations are also the same for men due to the gender division of labour, although women and gender minorities are disproportionately impacted by the Wagamama culture. Men are expected to be strong and brave. For instance, after the 2011 Great East Japan Earthquake, men struggled to express their feelings and vulnerability to their families and relatives. As a coping mechanism, some men went to sex workers to unburden their physiological distress.  Likewise, even elderly women were feared seeking help as they did not want to be called Wagamama in the times of crisis as there were bigger needs and community harmony was more important than their own needs, so they suffered but did not ask for help.

Despite all that has been done to recognise gendered social norms and their impacts on people, there is still a lot of work to be done in DRR. It is important to understand both spoken and unspoken social and cultural norms and their impacts on people’s everyday lives for inclusive DRR. In this short blog, we discussed some of the examples of Wagamama and its impacts on people’s everyday lives. We are currently working on a full paper where we analyse more cases to illustrate this concept, so watch this space.

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Dr Punam Yadav is Associate Professor of Humanitarian Studies and Co-director of the Centre for Gender and Disaster at the Institute for Risk and Disaster Reduction, University College London. Click here to learn more about her work.

Dr Miwako Kitamura is an Assistant Professor at the International Research Institute of Disaster Science (IRIDeS) at Tohoku University, Japan. She is one of the founder of a non-profit organization dedicated to supporting special minorities and people with disabilities in disaster.

An interesting map was published by the US Geological Survey shortly after the Turkish-Syrian earthquakes.1 It showed (perhaps somewhat predictively) that there was only one tiny square of the vast affected area in which Modified Mercalli intensity (which is largely a measure of damage) reached 9.0, the ‘violent’ level.2 This is–just about–enough to damage very significantly a well-engineered structure (but not necessarily enough to bring it crashing down). Although the disaster of 6th February 2023 produced, in fact, stronger shaking than this, it should not have caused 5,500 large buildings to collapse. The disaster in Turkey and Syria is very obviously the result of poor construction. This is painfully visible in the video images of buildings collapsing. The patterns of collapse are also the same as those in the last 20 Turkish earthquakes, although they are doubtless more extensive this time around. 

Building codes in Turkey have been upgraded five times in the last 55 years and are now perfectly good enough. The tragedy lies in their non-observance and the paucity of retrofitting. It is a mixture of simple errors, lax procedures, ignorance, deliberate evasion, indifference to public safety, untenable architectural fashions, corruption and failure to enforce the codes. Many, perhaps most, people in Turkey live in multi-storey, multiple occupancy reinforced concrete frame buildings. It is these that collapse. Most of them are highly vulnerable to seismic forces. There is plenty of engineering literature on the typical seismic performance defects of such buildings in Turkey. Perhaps we can grant a small exception for Syria, although before the civil war it did have building codes and earthquake research. However, the comment by a leader of the Syrian Catholic Church that buildings had been weakened by bombardment was something of a red herring. This probably affected about 2-3% of those that collapsed. 

 To know whether a reinforced concrete building is safe to live in would require knowledge of:

• the shear resistance (i.e., quality) of the concrete 
• the presence or absence and connectivity of shear walls 
• whether there are overhangs or other irregularities of plan that distribute the weight of the building unevenly or concentrate load on particular parts of it 
• the presence or absence of a ‘soft-storey’ open ground floor which concentrates the load above columns that cannot support it during seismic deformation 
• the connections between beams and columns, especially how the steel reinforcing bars are bent in 
• whether there are proper hooks at the end of rebars on concrete joints 
• whether the rebars were ribbed or smooth 
• the quality of the foundations and the liquefaction, landslide or subsidence potential of the underlying ground 
• the state of maintenance of the structural elements of the building 
• any subsequent modifications to the original construction. 

 An experienced civil engineer could evaluate some of that by eye, but much of the rest is hidden and only exposed once the building collapses. A short bibliography of sources is appended at the end of this article. 

Many of the news media that have reported the disaster have presented it as the result of inescapable terrestrial forces. While that cannot be negated, it is less than half of the story. The tragedy was largely the result of highly preventable construction errors. Vox clamantis in deserto: to examine this aspect of the disaster one would have to face up to difficult issues, such as corruption, political decision making, people’s expectations of public safety, fatalism versus activism, and more. How much simpler to attribute it all to anonymous forces within the ground! 

A well-engineered tall building that collapses will leave up to 15% void spaces in which there may be living trapped victims. It was notable that, in many buildings that pancaked in Turkey and Syria, the collapses left almost no voids at all, thanks to the complete fragmentation of the entire structure. This poses some serious challenges to search and rescue. In some cases the collapse was compounded by foundation failure, leading to sliding or rotation of the debris. 

There was also an interesting dichotomy in the images on television between the “anthill” type of urban search and rescue, carried out by people with no training, no equipment and no idea what to do, and professional urban search and rescue (USAR), which sadly was in the minority of cases. Nevertheless, it remains true that the influx of foreign USAR teams is, sadly, both riotously expensive and highly inefficient, as they tend to arrive after the ‘golden period’ of about 12 hours in which people could be rescued in significant numbers. 

Among the damage there is at least one classic example of the fall of a mosque and its minaret, the same as that which happened in the Düzce earthquake of 1999. Mosques are inherently susceptible to collapse in earthquakes: shallow arches, barrel vaults, rigid domes and slender minarets. The irony is that the great Turkish architect of the 16th century, Mimar Sinan (after whom a university in Istanbul is named) had the problem solved. He threaded iron bars through the well-cut stones of his minarets, endowing them with strength and flexibility. It is also singular that one of the first short, stubby minarets in Turkey (located in Izmir) was built 300 years after Sinan died in 1588. 

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Select Bibliography of Sources on Turkish R/C Construction Practices 

Cogurcu, M.T. 2015.Construction and design defects in the residential buildings and observed earthquake damage types in Turkey. Natural Hazards and Earth System Sciences 15: 931-945. 

Dogan, G., A.S. Ecemis, S.Z. Korkmaz, M.H. Arslan and H.H. Korkmaz 2021. Buildings damages after Elazığ, Turkey earthquake on January 24, 2020. Natural Hazards 109: 161-200. 

Dönmez, C. 2015. Seismic performance of wide-beam infill-joist block RC frames in Turkey. Journal of Performance of Constructed Facilities 29(1): 1-9. 

Erdil, B. 2017. Why RC buildings failed in the 2011 Van, Turkey, earthquakes: construction versus design practices. Journal of Performance of Constructed Facilities 31(3):  

Korkmaz, K.A. 2009. Earthquake disaster risk assessment and evaluation for Turkey. Environmental Geology 57: 307-320. 

Ozmen, H.B. 2021. A view on how to mitigate earthquake damages in Turkey from a civil engineering perspective. Research on Engineering Structures and Materials 7(1): 1-11. 

Sezen, H., A.S. Whittaker, K.J. Elwood and K.M. Mosalam 2003. Performance of reinforced concrete buildings during the August 17, 1999 Kocaeli, Turkey earthquake, and seismic design and construction practise in Turkey. Engineering Structures 25(1): 103-114.

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David Alexander is Professor of Risk and Disaster Reduction. He has conducted research on disasters since 1980. His main foci of interest are emergency management and planning, earthquake science, disaster epidemiology, and theoretical issues in disaster risk reduction.

Note from editor: We offer our commiserations to all those affected by the tragic events of this week. UCL staff and students can find support here. Find out where and how to donate to the earthquake appeal here.

Earthquake-induced direct and indirect losses tend to be high in highly populated earthquake-prone areas, especially in countries where most of the existing buildings and infrastructure are designed or built according to pre-seismic codes (if any). Therefore, there is a dire need to develop holistic strategies for mitigating and managing seismic risk. On the one hand, this involves risk understanding and quantification (e.g., risk/loss assessment methodologies). On the other hand, there is a crucial need to develop and implement strategies and techniques for repairing and retrofitting existing structures, which should be structurally effective, easy to apply, cost-effective, possibly reversible, and respectful of the architectural, heritage and cultural conservation requirements.

Both in the “diagnosis” and the “prognosis” phases, procedures to assess the structural performance under earthquake loads are paramount. Among many possibilities within the literature, choosing an appropriate assessment procedure depends on a simplicity vs accuracy trade-off governed by technical, economical, and time constraints. Moreover, various stakeholders have different needs on this matter: private owners likely need a detailed assessment focused on individual buildings or small portfolios, while government agencies or (re)insurance companies might look at large portfolios tolerating a lower refinement level and accepting higher uncertainties.

It is fundamental to select a procedure that can highlight the structural weaknesses of the considered structural system, so that it is possible to design retrofit solutions to specifically fix those. One procedure complying with this requirement, while being easy to apply, is SLaMA – Simple Lateral Mechanism Analysis.

Although SLaMA is normally applied using spreadsheets, it allows for defining the nonlinear force-displacement capacity and the sequence of local and global mechanisms of a building. It was introduced for the 1st time in the 2006 version of the New Zealand Society of Earthquake Engineering, NZSEE, Guidelines for the “Assessment and Improvement of the Performance of buildings in earthquakes” (NZSEE 2006), and revamped in the 2017 version (NZSEE 2017), after a substantial amount of research (Gentile 2017, Pampanin 2017; Del Vecchio et al. 2018; Gentile et al. 2019;  Gentile et al. 2019a; 2019b; 2019c; Bianchi et al. 2019). SLaMA is essentially mandatory in New Zealand, since it is required as an essential step before any other seismic numerical analysis is carried out. Its scope, however, is geographically much larger: more than 15 world-class companies (in New Zealand, Italy, Netherlands, UK) are using this method.

“SLaMA Solver Frame” is a free Windows/MacOS app created to enable engineers applying SLaMA using a graphical user interface, and without the need to create ad hoc spreadsheets. This app refers to reinforced concrete frame buildings, which constitute a substantial portion of the building stock in many countries around the world.

As shown in the tutorial video below, SLaMA Solver Frame is completely standalone (i.e., it does not require any other software to be run). It provides a “type and check” environment, in which every time the user inputs a parameter, the app automatically updates specific plots, therefore allowing for continuous cross checks and minimising input error. For each beam and column, SLaMA solver Frame provides their expected failure mode (flexure, bar buckling, shear, lap splice). For each beam column joint sub-assembly within the frame, the app determines its hierarchy of strength, indicating the member-level mechanism that causes its failure. Finally, by composing the results of each sub-assembly, SLaMA solver Frame provides an estimation of the plastic mechanism and the non-linear force-displacement curve.

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SLaMA Solver Frame can be downloaded for free (for Windows and MacOS) at https://www.robertogentile.org/en/slamaf/. If you find any bugs, or you have any suggestions/comments, please feel free to report them dropping an email to robstructuralapps@gmail.com.

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Disclaimer for SLaMA Solver Frame

SLaMA Solver Frame is provided by Dr Roberto Gentile under the Creative Commons “Attribution-No Derivatives 4.0 International” License. The purpose of SLaMA solver Frame is to cross-check by hand or spreadsheet calculations. This software is supplied “AS IS” without any warranties and support. The Author assumes no responsibility or liability for the use of the software. The Author reserves the right to make changes in the software without notification. The Author also make no representation or warranty that such application will be suitable for the use selected by the user without further calculations and/or checks.

 

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Roberto Gentile is a Lecturer in Crisis and Catastrophe Modelling at IRDR.

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References

Bianchi, Ciurlanti, and Pampanin. (2019). A SLaMA-Based Analytical Procedure for the Cost/Performance-Based Evaluation of Buildings. In COMPDYN 2019 – 7th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering. Crete Island, Greece.

Del Vecchio, Gentile, Di Ludovico, Uva, and Pampanin. (2018). Implementation and Validation of the Simple Lateral Mechanism Analysis (SLaMA) for the Seismic Performance Assessment of a Damaged Case Study Building [Open Access]. Journal of Earthquake Engineering 24 (11): 1771–1802. https://doi.org/10.1080/13632469.2018.1483278.

Gentile (2017). Extension, refinement and validation of the Simple Lateral Mechanism Analysis (SLaMA) for the seismic assessment of RC structures. PhD thesis. Polytechnic university of Bari, Italy.

Gentile, Pampanin, Raffaele, and Uva. (2019). Analytical Seismic Assessment of RC Dual Wall/Frame Systems Using SLaMA: Proposal and Validation [Open Access]. Engineering Structures 188: 493–505. https://doi.org/10.1016/j.engstruct.2019.03.029.

Gentile, Pampanin, Raffaele, and Uva. (2019). Non-Linear Analysis of RC Masonry-Infilled Frames Using the SLaMA Method: Part 1—Mechanical Interpretation of the Infill/Frame Interaction and Formulation of the Procedure [Open Access]. Bulletin of Earthquake Engineering 17 (6): 3283–3304. https://doi.org/10.1007/s10518-019-00580-w.

Gentile, Pampanin, Raffaele, and Uva. (2019). Non-Linear Analysis of RC Masonry-Infilled Frames Using the SLaMA Method: Part 2—Parametric Analysis and Validation of the Procedure [Open Access]. Bulletin of Earthquake Engineering 17 (6): 3305–26. https://doi.org/10.1007/s10518-019-00584-6.

Gentile, Del Vecchio, Pampanin, Raffaele, and Uva. (2019). Refinement and Validation of the Simple Lateral Mechanism Analysis (SLaMA) Procedure for RC Frames [Open Access]. Journal of Earthquake Engineering. https://doi.org/10.1080/13632469.2018.1560377.

New Zealand Society for Earthquake Engineering (NZSEE). (2006). Assessment and improvement of the structural performance of buildings in earthquakes. Wellington, New Zealand.

New Zealand Society for Earthquake Engineering (NZSEE). (2017). The Seismic Assessment of Existing Buildings – Technical Guidelines for Engineering Assessments. Wellington, New Zealand.

Pampanin. (2017). Towards the Practical Implementation of Performance-Based Assessment and Retrofit Strategies for RC Buildings: Challenges and Solutions. In SMAR2017- Fourth Conference on Smart Monitoring, Assessment and Rehabilitation of Structures. 13-15 March 2017. Zurich, Switzerland.

 

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

 

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.

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.

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).

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.

 

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 28^thDecember 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

 

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.

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