Student Profile: Yi-Wun Mika Liao

Developing physics-based modelling of synthetic earthquakes to access and forecast fault rupture, ground shaking, tsunami and landslides


June 2021

I was born and raised with two siblings by my grandparents in Taiwan. I graduated from the Department of Earth Science of National Central University, Taiwan, and studied ground motion simulation of historical earthquakes during my master’s years. After I got my master’s degree, I worked as a research assistant for several years. I’ve been thinking whether to get a PhD or not for many years. Therefore I recommended myself when one of my current supervisors, Dr Bill Fry, visited Taiwan and said he was calling for PhD students. The topic of the PhD project and the beauty of New Zealand are both so attractive to me, so I decided to join the project after talking to my supervisor.

I am a fluffy animal lover, especially dogs and cats. I like to hike although I don’t have many chances to hike in Taiwan because there are too many frogs and snakes in the mountains. Due to the Covid-19 pandemic, I am still waiting for the border restriction to be lifted. I am keen to go to New Zealand and hike in the frog-and-snake free mountains!

 

My project

Determining the input parameters for hazard assessment, such as recurrence interval of earthquakes for a given magnitude, rupture initiation on the fault, and probability of multiple-segment rupture, is quite difficult, especially for large earthquakes due to the short time period of our earthquake records. Physics-based earthquake simulators are one solution to this problem. Since our goal is to increase resilience to earthquakes, it is important to understand the possible recurrence interval of these events from a simulated catalogue of earthquakes, spanning more than 50,000 years. The aim of my project is to develop the modelling of synthetic earthquakes and generate simulated earthquake catalogues with a physics-based earthquake simulator, RSQSim.

New Zealand and Taiwan are both located at subduction zones and have high seismicity. Seismic hazard assessment is mandatory for both countries. Since I am still in Taiwan and more familiar with Taiwanese data, I am first trying to simulate the synthetic earthquakes with the seismogenic structures of Taiwan. By trying different values of the input parameters of RSQSim, such as initial stress, and comparing the results with the observed earthquake catalogue, I have learned what types of input values lead to the most realistic results. However, the simulated earthquake catalogues still couldn’t fit the observed one perfectly. There are some ways to improve the simulated catalogues, like adding more seismogenic structures and constraining more of the input parameters of RSQSim. This part would be more challenging.

 

Next steps

One of the next steps is to apply what I have learned from the Taiwanese data to New Zealand. As mentioned above, the improvement of seismogenic structures and constraint on the input parameters could be also one of the next steps. I hope that some realistic earthquake catalogues could be generated, and that this will help to assess the likely frequency of earthquakes and their related hazards.

 

Impact case study:

Model and tools for decision-making

 


How did Resilience Challenge research have an impact in 2019-2020?

 

Central to our mission to accelerate natural hazard resilience is the development of new models and tools to quantify hazards and impacts in more realistic ways, providing better assessments of resilience options to decision-makers.

Development of new models is iterative, requiring repeated testing and validation, and their application usually comes at the end of an extensive period of development. RNC is driving meaningful enhancements and innovations in this area, building on work in Phase 1, the Natural Hazards Research Platform, and leveraging existing New Zealand tools such as RiskScape and MERIT.

Updated hazard map for Whakapapa skifield. Credit: GNS Science

Earlier this year, Volcano programme research was integrated into updated hazard posters  for Turoa and Whakapapa skifields, as part of a collaboration with the Department of Conservation. Researchers were also commissioned by Ruapehu Alpine Lifts to produce a technical report on potential lahar hazard in the Whakapapa ski area. A new lahar simulation model, calibrated to previous lahars, was used to estimate the lahar footprint and impact for a range of scenarios. Results of the report have been used to develop safety measures for the new Sky Waka gondola.

 

 

Dr Nicky McDonald and colleagues from ME Research produced economic modelling utilising the MERIT (Measuring the Economics of Resilient Infrastructure Tool) capability developed in Phase 1, to assess the economic consequences of fuel outage scenarios following the Auckland-Marsden Point fuel pipeline failure. MERIT was applied to five disruption scenarios, which were then evaluated with and without mitigation options to better understand the impact of disruption and potential value of mitigation actions for New Zealand. The report was prepared for MBIE and findings also contributed to the Board of Inquiry into the 2017 Auckland Fuel Supply Disruption.

As part of our Coastal Flooding project led by Prof Karin Bryan (University of Waikato) and Dr Scott Stephens (NIWA), Dr Shari Gallop and Masters student Akuhata Bailey-Winiata (Te Arawa, Ngāti Tūwharetoa) carried out a summer project to determine the proximity of coastal marae (located within 2km of the coast) to coastal and river waterbodies. They found that 93% of coastal marae are located in the North Island; over 45% of coastal marae are within 200 meters of the coastline; and approximately 70% of coastal marae are located below 20 meters elevation relative to mean sea level. Data will be used as a baseline for determining risk and vulnerability of coastal marae to coastal hazards and sea-level rise. Akuhata’s research was recognised by the New Zealand Coastal Society who awarded him with a Māori and Pacific Island Research Scholarship in July 2020. 

Our Built Environment programme has completed new hazard maps for Bay of Plenty marae (showing fault lines, flooding, geothermal, liquefaction, and tsunami zones) using data from Rotorua City Council and Environment Bay of Plenty. The maps were provided to Te Arawa Lakes Trust collaborators, and are intended to be used to catalyse conversations with marae regarding adaptation and preparedness planning.

Part of our Weather and Wildfire programme involves the modelling of credible ‘what-if’ scenarios. What if the path of ex-Tropical Cyclone Cook (which did much damage in eastern Bay of Plenty in 2017) had been further west and hit our biggest population centre, Auckland? Weather scenario modelling at such fine-grid resolutions is a first for New Zealand, and allows detailed impact modelling to be carried out for a variety of coincident weather, flood, and landslide hazards, building a credible worse-case impact scenario for Auckland and surrounding districts. The early modelling is highlighting the potential for extreme impacts in Auckland, and in other areas well away from Auckland such as the higher elevations of the Kaimai ranges.

 

New modelling shows what could have happened if ex-TC Cook has tracked over Auckland. Credit: Ian Boutle, 2020

The primary goal of our Earthquake-Tsunami programme is to generate synthetic earthquakes using computer models. Big earthquakes and tsunamis (thankfully) don’t happen very often. A downside of this infrequency is that limited information from past earthquakes makes the job of forecasting future earthquakes and tsunamis challenging. One way of getting over these limitations is to generate synthetic earthquakes over millions of years using computer programs.

The team, led by Dr Bill Fry and Prof Andy Nicol, now has a first iteration of a synthetic seismicity model for New Zealand that incorporates all of the faults used for the National Seismic Hazard Model. This is a successful proof of concept. Further, through extended international collaboration, they have produced basic ground motion predictions from this model. This is an exciting and important stepping-stone in a programme of work that aims to improve future earthquake, tsunami and landslide hazard models in New Zealand.

 

This case study was submitted to the Ministry of Business, Innovation and Employment as part of our 2019-2020 annual reporting. 

 

Q & A with Prof Andy Nicol

 


 

Q. Tēnā koe Andy. Can you tell us a bit about how you got into geology, and how your research career has progressed?

I feel incredibly fortunate to have a career in research and teaching. I was encouraged by my family to attend university at a time when there were few financial barriers and, as a young person, many opportunities to find your way in life. In my first year at university I picked a range of subjects which included earth sciences. As it turned out earth sciences was something that I really enjoyed, which was probably not a great surprise given that I loved being in the mountains and spent many years listening to my grandfather talking about his soil science work.

I really thrived on self-directed research where it was possible to test ideas and to look at the world as it was millions of years ago. By the time I finished I’d been at university for 8 years and people were starting to ask “when are you going to get a real job”. Looking back there was no grand plan of what a real job might look like and, if I’m honest, I caught quite a few lucky breaks along the way.

After my PhD I secured post-doctoral positions in the Fault Analysis Group at Liverpool University (UK) and then at GNS Science. These jobs opened my eyes to the possibilities of research and exposed me to fantastic people, many of whom I am still working with and are good friends. Any success that I might have had in earth sciences can be attributed to the high calibre of these collaborators, to a fascination of the earth and to having a fair measure of tenacity.

Q. You’re now a Professor of Structural Geology at the University of Canterbury. How have you found the transition to university teaching, after many years at GNS Science?

As is the case for many new lecturers, preparing new teaching material is challenging, even if you are like me and had a lot of help from others. Teaching is great fun and gives me the opportunity to paint my fingernails and break frozen Mars bars, which I hope helps the students understand rock deformation and plate tectonics (my finger nails grow at the same rate as plate motion in Christchurch). Research at Crown Research Institutes (CRIs) and universities is very similar. One of the many great things about GNS Science is that it has many experts in different fields of earth science under the same roof, which is scientifically invigorating and promotes strong cross pollination. I am fortunate that I have continued to work closely with GNS scientists and have been able to marry this work with the scientific freedom and expertise offered by the university system. I think that New Zealand research would benefit greatly if we could promote stronger links between CRIs and universities.


Q. You’re co-leading the Resilience Challenge Earthquake-Tsunami programme. What aspect of the programme excites you most?

I am excited by the prospect of being able to conduct research that will help improve understanding of hazards and benefit all New Zealanders.

Q. The primary goal of the Earthquake-Tsunami programme is to generate synthetic earthquakes using computer models. How did the team get started on the path towards synthetic seismicity?

One of the thankful aspects of natural earthquakes and tsunamis is that the big ones don’t happen very often. The down side of this infrequency is that getting information on more than a couple of earthquakes for individual faults is relatively rare. Limited information from past earthquakes makes the job of forecasting future earthquakes and tsunamis challenging. One way of getting over these limitations is to generate synthetic earthquakes over millions of years using computer programs, which have been developed over the last 30 years. The current Earthquake-Tsunami programme is the culmination of discussions between seismologists and earthquake geologists over last few years. We think that synthetic earthquakes tested against real earthquakes are likely to be the way of the future, and the present programme represents an important stepping-stone for us to improve future earthquake, tsunami and landslide hazard models in New Zealand.

Q. You’ve studied the faulting in the 2016 Kaikōura earthquake extensively. How has that event shaped your current research interests?

An unfortunate truism about earthquakes is that you need to have them to understand them. I found the resilience and generousity of the farming community following the Kaikōura earthquake inspirational. The earthquake is distinguished by the number and complexity of faults that ruptured; many consider the Kaikōura earthquake to be the most complex surface rupture worldwide in the last 150 years. Despite this complexity, it is clear from other historical earthquakes that complex faulting has been very common historically in New Zealand. Understanding why complex earthquakes occur, testing to see if we can generate these earthquakes with our computer models and determining how they impact the timing and size of future earthquakes is a major focus of our work. We are hoping that ongoing studies of the faults that ruptured in the Kaikōura earthquake and computer modellings will provide value insights to these questions.

Q. What do you like to do outside work?

For many years I enjoyed spending time with my family and helping raise our two daughters, who have become awesome people. In recent years I have spent time travelling and, unfortunately, generating a sizeable carbon footprint. I also enjoy working with wood and have constructed many low-tech wooden structures, often with a lot of help from YouTube and my brother, who actually knows what he is doing.

Q. What are your future research ambitions?

Our research ambitions need to have stretch. The holy grail of earthquake research is to improve earthquake forecasting, which is many years behind weather forecasting. In New Zealand we are already using statistical analysis to forecast earthquakes on some faults and I have no doubt that with a better understanding of earthquake processes these forecasts will improve. This view is not held by all of my colleagues, and some will likely question my sanity for raising this subject. While better forecasts may be decades away, they have the potential to significantly improve our resilience to earthquake and tsunami hazards and, for me, is an important ambition.

 

 

Q & A with Dr Bill Fry

17/12/19


 

Q: Congratulations on your recently completed Hochstetter Lecture tour – how did it go?

Great! It was truly a rewarding and humbling experience. The audiences throughout the regions were as varied as the New Zealand landscape. However, the uniting characteristic was the genuine thirst for knowledge. I’ve been interacting with the New Zealand public for over a decade and I never fail to be impressed by the high level of understanding of geohazards and the keen desire to take on new science.

Q. You’re a seismologist and you also work a lot on tsunami hazards – how did you arrive at your current field of research?

I started my career in fundamental (academic) seismology, with very little focus on geohazards or societal application. Moving to New Zealand in 2008 changed all of that. I was fortunate enough to get a job with GNS as a civil servant, monitoring and responding to earthquakes. Almost immediately, the Mw7.8 Dusky Sound earthquake happened and my first real event response began. I was told that it was a “once in a career event”. Ha! The next decade produced three more M7+ earthquakes in New Zealand and a handful of tsunami responses. Once I saw tangible societal benefit in science and the true power of “science to practice”, there was no turning back.

Q: Your Hochstetter talk focussed on Kermadec trench earthquakes, and their potential to generate large tsunami for Aotearoa New Zealand. What are the major takeouts from this research?

Natural warning self evacuation (Long or Strong, Get Gone) is absolutely crucial to protecting coastal communities from many local tsunami-generating earthquakes. However, we’ve also documented local and regional tsunami-generating earthquakes that require a combination of natural warning, and science-based instrumental warning to keep coastal communities safe. The talk brought together geophysical observations, numerical simulations and observations of New Zealand citizens to highlight improvements that can be made to our tsunami response plans.


Q. You’re co-leading the Earthquake-Tsunami theme for Phase 2 of the Resilience Challenge. Can you talk us through the main projects in this theme?

Sure. The biggest challenge of putting hard numbers to seismic hazard in New Zealand is overcoming the limits of having a very short record of earthquakes. To capture the full range earthquake behaviour, we’d need to record earthquakes for tens of thousands of years. We obviously can’t do that (modern GeoNet recording only goes back to about 2001). Our theme will use our understanding of the physics of earthquakes and specific knowledge of New Zealand’s faults and tectonics to computationally model hundreds of thousands of years of earthquakes. We’ll look for earthquake sequences in those models that look like what we’ve seen over the last decade, and then see if subsequent earthquakes in the model inform us about what we might expect to see over the next 50 years. We’ll also evaluate whether this type of earthquake catalogue can underpin next-generation hazard models.

Q. How have the Canterbury and Kaikōura earthquakes affected the priorities for earthquake research?

When you see first hand the impact of these sequences on local communities, the need for applied research is absolutely obvious. One of the main changes that was driven by both of the sequences is the understanding that hazard before the event is not the same as hazard after the event. We’ve become better and better at using science to inform future hazard following big earthquakes. We’ve also become better at quantifying the influence of differences in geology and the particular characteristic of individual earthquakes on the resulting strong ground shaking.

Q. The research involving synthetic earthquakes has led to collaboration with colleagues in Taiwan. Can you tell us more about this collaboration?

For the last six or eight years, we’ve had a close three-nation collaboration with Taiwan and Japan that has focused on seismic hazard. All three countries face similar geohazard challenges. Through this collaboration, we’ve realised that many of the benefits of our RNC2 research program are also applicable to Taiwan. We decided to move forward together, pooling our talents to make better outcomes for both counties.

I recently undertook a visiting professor position in Taiwan to help launch the project and now both we and Taiwan are well on our way.

Q. Looking beyond Phase 2 of the Challenge, what future avenues of research would you like to pursue?

I’m particularly interested in understanding the ways in which we can use sophisticated geophysical analyses (that we currently only apply in academic ways well after the response need has passed) to produce real-time products that can be used to save lives, limit risk and improve recovery as the event is happening and immediately after it.