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.

 
 
 
 

How can we stop city breaks killing our cities?

This couple may look happy, but they’re destroying Barcelona. Image: Getty.

Can’t wait to pack your bags and head off on holiday again? It used to be that people would look forward to a long break in summer – but now tourists have got used to regular short breaks through the year. We love to jet off to the world’s glittering cities, even if only for a day or two. The trouble is, binge travelling may be killing the places we visit.

You may even have seen some “tourists go home” graffiti on your last trip, and it’s not hard to see why. Barcelona is a good example of how a city can groan under the weight of its popularity. It now has the busiest cruise port, and the second fastest growing airport in Europe. Walking through the Barcelona streets at peak season (which now never seems to end) flings you into a relentless stream of tourists. They fill the city’s hot spots in search of “authentic” tapas and sangria, and a bit of culture under the sun. The mayor has echoed residents’ concerns over the impact of tourism; a strategic plan has been put in place.

It is true though, that cities tend to start managing the impact of tourism only when it is already too late. It creeps up on them. Unlike visitors to purpose-built beach destinations and national parks, city-break tourists use the same infrastructure as the locals: existing systems start slowly to stretch at the seams. Business travellers, stag parties and museum visitors will all use existing leisure facilities.

‘Meet the friendly locals’, they said. Image: Sterling Ely/Flickrcreative commons.

Barcelona may only be the 59th largest city in the world, but it is the 12th most popular with international visitors. Compared to London or Paris, it is small, and tourism has spiked sharply since the 1992 Olympics rather than grown steadily as in other European favourites like Rome.

Growth is relentless. The UN World Tourism Organisation (UNWTO) even speaks about tourism as a right for all citizens, and citizens are increasingly exercising that right: from 1bn international travellers today, we will grow to 1.8bn by 2030, according to UNWTO forecasts.

Faced with this gathering storm, just who is tourism supposed to benefit? Travellers, cities, residents or the tourism industry?

Market forces

Managing the impact of tourism starts by changing the way destinations market themselves: once the tourists arrive, it’s too late. Tourism authorities need to understand that they are accountable to the city, not to the tourism industry. When the city of Barcelona commissioned the University of Surrey to look into how it might best promote sustainable development, we found a series of techniques which have been incorporated, at least in part, into the city’s 2020 Tourism Strategy.

In the simplest terms, the trick is to cajole tourists into city breaks which are far less of a burden on the urban infrastructure. In other words, normalising the consumption of sustainable tourism products and services. In Copenhagen, 70 per cent of the hotels are certified as sustainable and the municipal authority demands sustainability from its suppliers.

Higher than the sun. A primal scream from the world’s cities? Image: Josep Tomàs/Flickr/creative commons.

Destinations must also be accountable for the transport impact of their visitors. The marketing department might prefer a Japanese tourist to Barcelona because on average they will spend €40 more than a French tourist – according to unpublished data from the Barcelona Tourist Board – but the carbon footprint we collectively pay for is not taken into account.

Crucially, for the kind of city breaks we might enjoy in Barcelona, most of the carbon footprint from your holiday is from your transport. Short breaks therefore pollute more per night, and so destinations ought to be fighting tooth and nail to get you to stay longer. It seems like a win for tourists too: a few extra days in the Spanish sun, a more relaxing break, and all accompanied by the warm glow of self-satisfaction and a gold star for sustainability.


Destinations can also target customers that behave the most like locals. Japanese first-time visitors to Barcelona will crowd the Sagrada Familia cathedral, while most French tourists are repeat visitors that will spread out to lesser-known parts of the city. Reducing seasonality by emphasising activities that can be done in winter or at less crowded times, and geographically spreading tourism by improving less popular areas and communicating their particular charms can also help reduce pressure on hot spots, much like Amsterdam is doing.

Turnover is vanity, and profit margins are sanity. No city should smugly crow about the sheer volume of visitors through its gates. If tourism is here to stay, then the least cities can do is to sell products that will have the greatest benefit for society. Whether it’s Barcelona, Berlin, Bologna or Bognor, there should be a focus on locally and ethically produced products and services which residents are proud to sell. Tourist boards should work with small businesses that offer creative and original things to do and places to stay, adding breadth to the city’s offering.

The ConversationWhether Barcelona will introduce these ideas will depend on the bravery of politicians and buy-in from the powerful businesses which are happily making short-term profits at the expense of residents and the planet. It is possible to do things differently, and for everyone to benefit more. It may be that the tipping point lies in the age-old mechanics of supply and demand: bear that in mind next time you’re booking a quick city break that looks like it’s only adding to the problem.

Xavier Font is professor of marketing at the University of Surrey.

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