The Iranian and Pakistani coast is rapidly urbanising. It's at risk of a tsunami

Iranian holidaymakers enjoy the Gulf resort of Kish in November 2016. Image: Getty.

That tsunamis can cause death and devastation has become painfully clear over the past two decades. On Boxing Day, 2004, a magnitude 9 earthquake off the coast of Sumatra caused waves several metres high to devastate the Indian Ocean – killing more than 230,000 people in 14 countries. In 2011, another magnitude 9 earthquake, this time off Japan, produced waves up to 20 metres in height, flooding the Fukushima nuclear reactor. It killed more than 15,000 people. The Conversation

A new study, published in Geophysical Journal International, by my colleagues and me suggests that a 1,000km long fault at the northern end of the Arabian Sea may pose a similar threat.

The Makran, as the southern coastal region of Iran and Pakistan is known, is a subduction zone. In such regions, one of the Earth’s tectonic plates is dragged beneath another, forming a giant fault known as a “megathrust”. As the plates move past each other, they can get stuck, causing stress to build up. At some point the stress becomes high enough that the megathrust breaks in an earthquake.

This was exactly what caused the Sumatra 2004 and Tohoku 2011 earthquakes. When a megathrust moves suddenly, the whole seafloor is offset and the water has to move out of the way over a huge area. This sets off waves with particular characteristics that can cross entire oceans: tsunamis. The phenomenon, along with their potentially large size, makes subduction zone earthquakes particularly dangerous.

The Makran region. Image: adapted from NASA photo.

But just because a part of a subduction zone produces earthquakes doesn’t mean that the whole megathrust can move in one go. We often see that stress builds up at different rates on different parts of the fault, with some parts sliding smoothly past each other. How much of a megathrust can move in one go is important because it determines the size of the resulting earthquake. The amount that the Makran megathrust can move in earthquakes has been a longstanding question, but the hostile climate and challenging politics of the region have made research there difficult.


We know that the eastern part of the Makran megathrust (in Pakistan) can produce large earthquakes. A magnitude 8.1 quake off the coast of western Pakistan in 1945 caused a tsunami which killed about 300 people along the coasts of Pakistan and Oman. There have been several smaller earthquakes on the megathrust since, including a magnitude 6 in February this year.

If the western part of the Makran (in Iran) also produces earthquakes – and the whole Makran megathrust were to move in one go – it could produce a magnitude 9 earthquake, similar to those in Sumatra and Tohoku.

However, we have never actually recorded a subduction earthquake in this part of Makran. In fact, there are only records of one candidate quake from 1483 – and the actual location of this is disputed. But it’s important to keep in mind that just because we haven’t seen an earthquake doesn’t mean that there couldn’t be one – particularly since the intervals between earthquakes are often hundreds or thousands of years. Historically, not many people have lived in the remote Iranian Makran, a desert which killed Alexander the Great’s army. So earthquakes might simply not have been documented.

GPS data

We used new data to look for tell-tale signs of a possible earthquake. Imagine a piece of paper on a table. If you hold one end and push the other end towards it, the paper crumples up and the distance between the two ends gets shorter. If you let go, the paper flattens out. The fixed end is like a megathrust which is stuck. Indeed, if the Arabian plate is stuck, and stress is building up, southern Iran will be squeezed and shortened. We can look for evidence of this shortening by using a more accurate version of the GPS systems found in smartphones. My coauthors from the National Cartographic Centre in Iran have set up a network of GPS stations to measure how fast different parts of Iran are moving relative to Arabia.

We found that the velocities fit with Iran being shortened near the coast, suggesting that stress is indeed building up – and meaning there could be a large subduction earthquake in the future. This fits with recent work looking at large boulders along the coast of Oman, thought to have been deposited by tsunamis. The locations of these boulders suggest that the tsunami which brought them there would need to have come from a subduction earthquake, either in western Makran or along the entire subduction zone – including Pakistan. These boulders were probably deposited in the last 5,000 years, but we can’t know for sure.

The 2004 Sumatra tsunami strikes Ao Nang, Thailand. Image: David Rydevik/wikipedia.

This is a hazard that people need to be aware of, particularly those living in coastal regions around the Arabian Sea. Rapid urbanisation along the Omani and Pakistani coasts in recent years has increased the population exposed to earthquakes and tsunamis in the Makran. Karachi, at the eastern end of the subduction zone, is now a megacity and home to around 25m people. Much of Muscat, the Omani capital, is less than 10 metres above sea level, making it vulnerable to tsunamis. The port of Gwadar in Pakistan, which was badly damaged in a 1945 earthquake, is also undergoing massive development.

To help protect these people, and make sure that they are properly prepared, we need to understand this hazard better. Education and early warning are both key – exercises testing the Indian Ocean Tsunami Warning System are a step in the right direction, especially if they engage the public.

At the moment, we can only say that a large earthquake in the Makran is consistent with the limited data which we have available. By continuing to work with scientists in Iran and Pakistan to make more measurements I hope that in the future we will have a much better idea of what to expect from this subduction zone.

Camilla Penney is a PhD Candidate in geophysics at the University of Cambridge.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

This app connects strangers in two cities across the world. But can it tackle urban loneliness?

New Delhi, in India, where many of Duet-App's users come from. Image: Ville Miettinen

“You can be lonely anywhere, but there is a particular flavour to the loneliness that comes from living in a city, surrounded by millions of people”. Olivia Laing, The Lonely City

Our relationship to where we live and the spaces we inhabit define who we are and how we feel. But how often do we articulate the emotional impact of this relationship, whether this be loneliness, frustration or even civic pride?

“When I moved to a new city, started living alone, wanted to drink less, stay indoors more, and when I realised that I cannot make any more best friends.”

A new social network, a simple app that connects two individuals from the UK and India, aims to counter some of these issues.  Over the course of a year connected pairs receive one question a day through the app and their responses are exchanged with each other. A simple interaction that gradually builds a series of one-on-one relationships and invites users to imagine, over time, the other person living their life.

Distant geographies are an implicit part of the experience, therefore many of the questions nudge users to explore correlations between their physical and emotional landscapes. The data shows us that many of the Duet-App users are located in populous urban cities like Delhi, Bangalore, Manchester, Leeds and London, places that can just as often discourage feelings of belonging and place-making as much as they foster them.

“I had thought I'd never be able to live here again. but here I am living again at home after almost a decade living elsewhere. Living in Mumbai is a contact sport, and I can't do without it's chaos and infectious energy.”

Mumbai, India. Image: Deepak Gupta

In general cities are getting bigger and spreading wider at the same time as our communications are increasingly being conducted online and via digital gateways.

There is a sense that much of our online personas project an idealised version of ourselves; we increasingly document and express our daily lives through a filter and we are not always comfortable with a spontaneous expression of ourselves. Duet-App seeks to foster alternative digital relationships that through their anonymity allow us to be more honest and free.

“I feel a lot of people assume that I always have a lot going on for me and everything's always happy and amazing. I wish they could appreciate... how much of my own anxiety I swim in every single day. I appear and behave “normal” on the outside, calm and composed but there are always storms going on in my head.”

In exploring the responses to the questions so far, those that often garner the most replies relate directly to how we feel about our personal position in the world around us. Often these questions act as provocations not only to share responses but to reflect and articulate our thoughts around how we feel about what we are doing in the here and now.

Manchester, another popular city for Duet-App users. Image: Julius 

“Sometimes I feel sad about it [getting old] because I saw how easy it would be to feel lonely, and the fact that the world is set up for able-bodied young people is a bit of a travesty.”

Although many social media platforms allow for distant engagement and access into the lives of others we are in the main still curating and choosing our friendship circles. Through Duet-App this is randomised (and anonymised) with the intention of bypassing the traditional mechanics of how we broker online relationships. While directly exploring the digital space as a place for intimacy.


“Where do you go for peace?

“Well the internet, really. I do some mindless browsing, peek into the fandoms, listen to a few songs. Calms me down.”

Snapshots into the lives of someone existing and playing out their lives remotely can highlight shared concerns that break down preconceptions of how life is lived by others. Prompted by the reflections of a stranger exposed to our lives, digital relationships can encourage us to address the physical space we inhabit and the effects that the cities we live out our lives in have on our own well being. 

Catherine Baxendale is director of Invisible Flock.

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