Newsletter 7 - September 2021

Haiti - 10 years after

On August 14, 2021, a magnitude (Mw) 7.2 earthquake (Mw) hit Haiti at 8:30 am local time, followed by numerous aftershocks. This earthquake is reminiscent of the 2010 earthquake with equivalent magnitude, which caused nearly 300,000 deaths, thousands of injuries, and economic losses greater than the GDP of the country, making it a major disaster.

There are many similarities between 2010 and 2021 earthquakes, and more specifically their magnitude and their location on the same fault system. However, there are two main differences: a geographical one and an operational one, the latter fully illustrating the need to consider all the components that make up a city in the prevention of seismic risk. And this is the URBASIS-EU project objective.

Located near Port-aux-Princes, the 2010 earthquake hit the major urban area of the island where goods, people and political and decision-making bodies are concentrated. The earthquake was exceptional, both in terms of the number of human casualties (victims, injured and homeless taken care of for several years) and in terms of the disorganization at the time of the crisis management as the operational bodies had been hardly impacted. The 2021 earthquake caused (in the last information) about 3,000 deaths and many building destructions (more than 50,000 houses damaged), disastrous consequences which are nevertheless less severe than the 2010 ones. These differences remind us of the need to integrate the vulnerability of urban exposed areas in any seismic risk reduction initiative.

After the 2010 earthquake, international emergency and development aid was mobilized. After the crisis management period, many academic, institutional or private sector collaborations were initiated and feedback from 2010 has enabled a more effective post-earthquake strategy to be put in place in 2021, avoiding the organizational difficulties observed in 2010 related to the influx of aid. It is known that the priority actions of international frameworks (such as Hyogo 2005-2015, Sendai 2015-2030, etc..) for disaster resilient nations and communities are bearing fruit, reducing losses and consequences. It should be noted that unlike the classical representations of risk as a combination of hazard, vulnerability and exposure, it is appropriate to add decision making as an integral part of the definition of risk, as described by Kerven in his definition of Cyndinics. Indeed, the upstream decisions of operators, managers or decision-makers considerably influence the magnitude of the disaster and must be considered accordingly in any risk study.

Integrating urban aspects into the research of seismic hazard and risk is then critical. For example, this includes urban fault-systems analysis, induced seismicity close to urban areas, wave propagation in a complex urban environment including site-city interactions, etc…. These are the main objectives of the URBASIS-EU project and the main topics of our 15 early stage researchers' PhD thesis.

  Edito by Philippe Guéguen, coordinator of the ITN URBASIS project.

Incoming URBASIS-EU scientific deliverables

Deliverable D3.1 - General guidelines to assess soil response in urban areas
Site response analysis in any area can be challenging due to complex 2D or 3D wave propagation and possible non-linear soil behaviour, etc. However, densely populated urban areas and industrial environments pose additional difficulties including among other high background noise level hindering usage of empirical seismic methods, the occurrence of strong local sources affecting the application of methods based on ambient noise. In addition, the lack of free space and low security in public areas can make site characterization more difficult. Last but not least, some methods cannot be successfully applied (heavy source active seismic) or are too expensive in an urban environment like the installation of borehole seismic monitoring stations. I described several methods for site analysis and site characterization indicating the problems that can be encountered in an urban environment. For some of the techniques, I presented very detailed real-life examples from our investigations in the city of Lucerne, including empirical methods and approaches based on ambient vibration.
Figure 1. On the left: diagram showing the principle of the Hybrid Standard Spectral Ratio method (SSRh – Perron, et al. 2018). On the right: amplification factors for 1.2Hz for the city of Lucerne estimated using the SSRh method.
Deliverable D1.2 - Ground-motion stochastic simulations in Europe
A spectral decomposition of the Fourier amplitude spectra is applied to determine the source parameters of earthquakes occurred in central-southern Europe. Using the event catalog from the International Seismic Centre (ISC), waveforms recorded in the target area since late ‘90s have been downloaded from the European Integrated Data Archive (EIDA). A non-parametric decomposition approach is applied to isolate source, propagation and site contributions, which introduce a regionalization for the attenuation model into two domains. For each domain, a spectral attenuation with hypocentral distance model is determined in a tabular form and used to remove regional specific propagation effects from the spectra of recordings. Once isolated from local site effects, the obtained source spectra are fitted to a standard w²-model to determine the seismic moment and the corner frequency of each earthquake, which in turn are used to compute the stress drop considering a circular rupture model with uniform stress drop. Outcomes of the spectral decomposition, attenuation, site amplification and source parameters, are incorporated with the ground motion stochastic simulations.
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Deliverable D3.5 - Updated release of SPEED for city seismic response investigations
Physics-based earthquake scenario simulations (PBS) are used to generate reliable site-specific ground motions considering fault rupture, path and site effects. Usually, the ground response from these scenarios is decoupled from buildings, thus neglecting the dynamic interaction of soil and structure (SSI). Past research points out the fact that SSI can modify both ground and structure response, especially in densely packed cities. One has to spend a large number of computational resources to model SSI. However, Full numerical coupling of 3D PBS with non-linear structural analyses of Multiple Degrees of Freedom (DOF) systems have already been proposed in the literature (Lu et al. 2008; McCallen et al. 2021a and 2021b). To extend these numerical methods to city-scale simulations, we have enhanced SPEED code (www.speed.mox.polimi.it) by developing new modules. In this updated code, one can model building on top of the soil as a single-DOF oscillator with a fixed base or a 4-DOF system to represent soil-foundation-structure. This code is validated by modelling clusters of structures in different configurations and considering soil heterogeneity. In addition to the updated SPEED code, a GUI pre/post-processing tool is also under development, so that the average user can analyse the results of a simulation. 

Figure 1: Conceptual framework for "source-to-structure" seismic wave propagation.

Deliverable D4.4 - Testing of site-amplification models used by GMMs
Ground Motion Models (GMMs) predict the probability of reaching a ground motion intensity on a site following an event, depending on the event source and path properties and the conditions at the site. Such models are generally developed using regression over several observations, but because ground motion datasets with a wide range of magnitude and distance have until recently been rare, the GMM predictions are rarely tested against independent data. Now, with increasingly larger datasets becoming available, testing procedures for GMMs have become more common. One example is the testing framework for by Loviknes et al. (2021) for GMM non-linear site amplification factors using a new dataset by Bahrampouri et al. (2020) consisting of ground motion records from the KiK-net network in Japan. This deliverable will summaries the state-of-the-art of testing procedures for GMMs and apply the testing framework of Loviknes et al (2021) to additional ground motion datasets.

Figure 1: Loviknes et al. (2021) tested four non-linear site amplification models and a linear site amplification model against the site response of individual well recording stations from the KiK-net network in Japan (Figure from Loviknes et al. 2021)

How about our ESRs?

Jaleena Sunny - ESR1.1

“ We were able to introduce a better metric for selection and ranking of models.”
 

"It is hard to believe that it’s been almost two years since we all started our PhD adventure. Yes! A very different two years far from our expectations. But I think we all managed to adapt with the new work environment quickly and took this as an opportunity to work smarter.


I am working with the selection, ranking and calibration of ground motion models. Hundreds of candidate models are available for various tectonic regions and assessing the predictive capability of a ground motion model and the selection of the best GMM for a given application from this growing suite of predictive models, therefore poses many challenges. We were able to introduce a better metric for selection and ranking of models. Now I am focussing more on calibration of empirical and stochastic models.


I feel myself fortunate to be a part of URBASIS and work with leading scientists and with my ESR friends. So excited to meet you all in person during our Winter School at Grenoble!"

Shoaib Ayjaz Mohammed - ESR3.3

“If not for the pandemic, I would never have imagined connecting with a large network in such a short time.”
 

"The past twenty months for me has been a period full of curiosity and learning, making new friends, and of course, making an insane amount of video calls. I consider myself fortunate to have started my doctoral studies just a month and a half before the total lockdown was announced in France. When I look back now, I realise that even this short time was crucial in setting up things and getting that initial boost after meeting fellow PhD students and other researchers at the lab. Figuring out ‘work from home’ during the teeth of the pandemic was not trivial, but also not too difficult at the same time. This has been a very interesting and different experience altogether. And that’s on top of the fact that doing a PhD itself is a unique one-time experience. If not for the pandemic, I would never have imagined connecting with a large network in such a short time, including peers from the seismology community and beyond. This experience I am having in the URBASIS project is truly enriching and I look forward to making use of this valuable opportunity as best as I can."

Pungky Suroyo - ESR2.1

“As the directions of our research become clearer, more questions arise.”

"Passing the 2nd year of PhD's life, more and more uncertainties are faced.  As the directions of our research become clearer, more questions arise. It causes me sometimes to feel uncertain that things will actually work out and once in a while that I am stuck in my research. In addition, the pandemic situation has forced several events and conferences to be postponed. It becomes another obstacle for ESR. Despite all the challenges, getting support from friends, other ESRs, supervisors, and the university help me to cope with the crisis. Besides, discovering new hobbies and activities helped me to stay productive and motivated.

With the current situation, which is getting better, and the restrictions that have been lifted, I am currently preparing myself to re-adapt to the offline teaching system, as well as preparing for several pending plans such as secondment and workshops. I'm anticipating and looking forward to the upcoming winter school and other URBASIS activities. Hopefully, with the ups and downs of PhD's life, all ESRs can adapt well and stay motivated in carrying out their research."

 

Incoming URBASIS-EU events

URBASIS-EU Winter School - Earthquake Engineering and Engineering Seismology
In the framework of the European ITN URBASIS-EU project, we are organizing a winter university on seismic risk in urban environments from January 24 to January 29, 2022, in Autrans, in the French Alpine Space.

The objective of this winter university is to provide students (PhD, post-doc and others) with an insight into research issues in seismology and engineering seismology in the broadest sense, and current and emerging research topics on seismic risk in interaction with the components that make up urban environments. Among these topics, we find the prediction of seismic ground motion and site effects, the emerging risk associated with induced seismicity, risk characterization and losses prediction, wave propagation in complex urban environments, etc...

Registrations are open until September 30, 2021.

More information & Registrations

 
URBASIS-EU Workshop 2 - Induced seismicity
The URBASIS workshop on Induced Seismicity will take place as a 3-day hybrid-online event hosted by the University of Liverpool, UK, from 4 – 6 October, 2021. Each day will comprise of 4-hour sessions. We expect most participants to access the course online, however, limited places may be available in Liverpool (subject to risk assessment and university approval). This workshop is targeted at a general scientific/engineering audience (no prior experience necessary!). The content will be a mixture of taught material and practical sessions with case-study applications. Topics include an introduction to earthquakes and induced seismicity, and the micro-seismicity imaging workflow. Participants will be guided through practical examples of induced seismicity monitoring using case-study data from various situations (thermal, excavation, injection, experimental). The workshop will be delivered by Applied Seismology Consulting, who have extensive expertise in the field of micro-seismic monitoring and analysis in commercial applications.

More information
Incoming URBASIS-EU WP meetings 
- WP1 #3 meeting on Low Probability / High Consequences earthquakes will be held on September 27 at 9am.
- WP2 #3 meeting on Induced Seismicity will be coupled with Workshop 2 
- WP3 #3 meeting on Urban seismology, engineering seismology and earthquake engineering will be held on November 24 at 2pm.

More information