How we discovered the conditions behind ‘slow earthquakes’ that happen over weeks or even months – new research


The world’s tectonic plates.
Naeblys/Shutterstock

Åke Fagereng, Cardiff University

You’re probably familiar with earthquakes as relatively short, sharp shocks that can shake the ground, topple buildings and tear rips in the Earth. These earthquakes, and their aftershocks, happen because although tectonic plates move at centimetres per year, this motion is seldom steady. Earthquakes result from a “stick-slip” motion, where rocks “stick” along fault planes while stress accumulates until a “slip” occurs – a bit like pulling on a stuck door until it suddenly opens. This slip also releases energy as the seismic waves that, in large magnitude earthquakes, create substantial damage.

In the last two decades another class of stick-slip motion has been discovered worldwide. These “slow slip events” last for weeks to months, compared to seconds to minutes for earthquakes. Slow slip events occur faster than average plate motion, but too slow to generate measurable seismic waves. This means they need to be studied by GPS networks rather then seismometers.

Although their motion is slow, the amount of movement that occurs in a slow slip event is substantial. Earthquake magnitude depends on the distance that rocks move and the area this movement occurs over. Using the same definition, many slow slip events would have had magnitudes above 7.0 if they slipped at earthquake speeds.

Slow slip events repeat at intervals of a year to a few years. Compared to major earthquakes, which have repeat times of hundreds of years (or more), slow slip events are actually very frequent. Even in the short time of a couple of decades that we’ve observed these types of slip, many cycles have occurred in several places – notably around the Pacific Rim.

Slow slip events generally happen next to areas where faults are locked and expected to rupture in major earthquakes. It’s therefore possible that these slow slip events can trigger earthquakes on neighbouring locked faults. It has, for example, been suggested that slow slip events preceded the 2011 magnitude 9.1 Tohoku earthquake in Japan and the 2014 magnitude 8.1 Iquique earthquake in Chile. That said, numerous slow slip events have also been observed without any immediate, subsequent major earthquakes on neighbouring faults.

Earthquakes may also trigger slow slip. In particular, the magnitude 7.8 Kaikōura earthquake in New Zealand in 2016 triggered slow slip events up to 600km away from its epicentre.

It is not known why some fault segments host slow slip and others host earthquakes. Neither is it known whether the same area can change behaviour and host either slow slip or earthquakes at different times. It’s therefore important to characterise the source of slow slip, and find out what materials help create slow slip and under what conditions.

A unique opportunity

The Hikurangi subduction zone.
Åke Fagereng composite using map data from NOAA., Author provided

The Hikurangi subduction zone (where the Pacific ocean floor is pulled underneath the New Zealand continent) offshore New Zealand’s North Island is potentially the country’s largest earthquake fault and is a unique opportunity to investigate slow slip events. This is because slow slip here happens shallower and closer to the shoreline than anywhere else in the world.

The drill.
Åke Fagereng, Author provided

The shallow slow slip events in New Zealand have been observed by onshore GPS and ocean bottom pressure sensors. Oceanic scientific drilling expeditions recently sampled sediments and installed observatories along this margin.

The subduction zone.
Stihii/Shutterstock

These International Ocean Discovery Program expeditions – which drilled to just over 1km deep in water depths of 3.5km in late 2017 and early 2018 – revealed that the seafloor rocks and sediments hosting slow slip in Hikurangi are extremely variable. The range of rocks, described in a recent Science Advances paper led by Philip Barnes of NIWA (New Zealand’s National Institute of Water and Atmospheric Research), include mudstones, sands, carbonates, and sedimentary deposits from oceanic volcanic eruptions. The seafloor samples show that the source of the slow slip is a mixture of very soft sediment and hard, solid rocks.

Different types of rock from the New Zealand seafloor.
Åke Fagereng, Author provided

The diverse seafloor sediments are not the only variability offshore of New Zealand. The seafloor itself is also very rough, including seamounts (submarine mountains rising over a kilometre above the seafloor). This seafloor roughness also makes the fault vary depending on where along it you are.

The observations are consistent with a hypothesis where slow slip events occur in rocks that are transitional between moving steadily and moving in earthquakes. One way to think of this model is as rigid rocks interacting with softer, more ductile surroundings. Researchers using numerical simulations and laboratory experiments have also suggested that variable fault rocks can cause slow slip.

But diverse fault rock isn’t the only model for the mechanics of slow slip. Another possibility is that pressurised fluids decrease frictional resistance and slip speed along faults. It is also possible that some rocks become stronger when they move faster – so that faults start accelerating but slow down before reaching earthquake speeds.

The recent discoveries in New Zealand may be applicable to other depths and locations around the world. However, future studies will undoubtedly lead to further insights and complexities – including in the relationship between slow slip events and earthquakes.The Conversation

Åke Fagereng, Reader, School of Earth and Ocean Sciences, Cardiff University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Electronic waste is recycled in appalling conditions in India



File 20190213 181604 ksgdan.jpg?ixlib=rb 1.1
The vast majority of e-waste in India is processed by hand.
Miles Parl, Author provided

Miles Park, UNSW

Electronic waste is recycled in appalling conditions in India

The world produces 50 million tonnes of electronic and electrical waste (e-waste) per year, according to a recent UN report, but only 20% is formally recycled. Much of the rest ends up in landfill, or is recycled informally in developing nations.




Read more:
Does not compute: Australia is still miles behind in recycling electronic products


India generates more than two million tonnes of e-waste annually, and also imports undisclosed amounts of e-waste from other countries from around the world – including Australia.

We visited India to examine these conditions ourselves, and reveal some of the devastating effects e-waste recycling has on workers’ health and the environment.

Obsolete computer electronics equipment lie stacked along the roads in Seelampur.
Alankrita Soni, Author provided

Indian e-waste

More than 95% of India’s e-waste is processed by a widely distributed network of informal workers of waste pickers. They are often referred to as “kabadiwalas” or “raddiwalas” who collect, dismantle and recycle it and operate illegally outside of any regulated or formal organisational system. Little has changed since India introduced e-waste management legislation in 2016.

We visited e-waste dismantlers on Delhi’s outskirts. Along the narrow and congested alleyways in Seelampur we encountered hundreds of people, including children, handling different types of electronic waste including discarded televisions, air-conditioners, computers, phones and batteries.

Open fires create toxic smoke, and locals reported high rates of respiratory problems.
Alankrita Soni, Author provided

Squatting outside shop units they were busy dismantling these products and sorting circuit boards, capacitors, metals and other components (without proper tools, gloves, face masks or suitable footwear) to be sold on to other traders for further recycling.

Local people said the waste comes here from all over India. “You should have come here early morning, when the trucks arrive with all the waste,” a trolley driver told us.

Seelampur is the largest e-waste dismantling market in India. Each day e-waste is dumped by the truckload for thousands of workers using crude methods to extract reusable components and precious metals such as copper, tin, silver, gold, titanium and palladium. The process involves acid burning and open incineration, creating toxic gases with severe health and environmental consequences.




Read more:
Almost everything you know about e-waste is wrong


Workers come to Seelampur desperate for work. We learned that workers can earn between 200 and 800 rupees (A$4-16) per day. Women and children are paid the least; men who are involved with the extraction of metals and acid-leeching are paid more.

Income is linked to how much workers dismantle and the quality of what is extracted. They work 8-10 hours per day, without any apparent regard for their own well-being. We were told by a local government representative that respiratory problems are reportedly common among those working in these filthy smoke-filled conditions.

Residential areas adjoining Seelampur Drain.
Alankrita Soni

Delhi has significant air and water pollution problems that authorities struggle to mitigate. We were surprised to learn that the recycling community does not like to discuss “pollution”, so as not to raise concerns that could result in a police raid. When we asked about the burning of e-waste, they denied it takes place. Locals were reluctant to talk to us in any detail. They live in fear that their trade will be shut down during one of the regular police patrols in an attempt to curb Delhi’s critical air and water problems.




Read more:
As another smog season looms, India must act soon to keep Delhi from gasping


As a result of this fear, e-waste burning and acid washing are often hidden from view in the outskirts of Delhi and the neighbouring states of Uttar Pradesh and Haryana, or done at night when there is less risk of a police raid.

Incidentally, while moving around Seelampur we were shocked to see children playing in drains clogged with dumped waste. During the drier months drains can catch fire, often deliberately lit to reduce waste accumulation.

Young boys searching for valuable metal components they can sell in Seelampur.
Author provided

After our tour of Seelampur we visited Mandoli, a region near Delhi where we were told e-waste burning takes place. When we arrived and asked about e-waste recycling we were initially met with denials that such places exist. But after some persistence we were directed along narrow, rutted laneways to an industrial area flanked by fortified buildings with large locked metal doors and peephole slots not dissimilar to a prison.

We arranged entry to one of these units. Among the swirling clouds of thick, acrid smoke, four or so women were burning electrical cables over a coal fire to extract copper and other metals. They were reluctant to talk and very cautious with their replies, but they did tell us they were somewhat aware of the health and environmental implications of the work.

We could not stay more than a few minutes in these filthy conditions. As we left we asked an elderly gentleman if people here suffer from asthma or similar conditions. He claimed that deaths due to respiratory problems are common. We also learned that most of these units are illegal and operate at night to avoid detection. Pollution levels are often worse at night and affect the surrounding residential areas and even the prisoners at the nearby Mandoli Jail.

Women extracting copper from electrical wires, in a highly polluting process.
Alankrita Soni, Author provided

We had the luxury of being able to leave after our visit. It is devastating to think of the residents, workers and their children who spend their lives living among this toxic waste and breathing poisonous air.

Field trips such as this help illustrate a tragic paradox of e-waste recycling in developed versus developing nations. In Australia and many other advanced industrialised economies, e-waste collection is low and little is recycled. In India, e-waste collection and recycling rates are remarkably high.

This is all due to informal recyclers, the kabadiwalas or raddiwalas. They are resourceful enough to extract value at every stage of the recycling process, but this comes with a heavy toll to their health and the environment.


This article was co-written by Ms. Alankrita Soni, UNSW Alumni & practising Environmental Architect from India.The Conversation

Miles Park, Senior Lecturer, Industrial Design, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Australia: El Nino Threat Easing


There is increasing good news as far as drought conditions are concerned in Australia, with the threat of an approaching El Nino diminishing.

For more visit the article linked to below:
http://www.reuters.com/article/2014/07/29/us-weather-elnino-idUSKBN0FY0DG20140729

Media Release: Myall Coast Beaches Closed to 4WDs


The link below is to a media release concerning the closure of Myall Coast beaches to vehicles due to weather conditions.

For more visit:
http://www.environment.nsw.gov.au/media/OEHmedia1306201300.htm

Myall Lakes National Park


Kevin's Daily Photo, Video, Quote or Link

It was my first official day of annual leave from work today and of course it had to start with a good sleep-in, which I might add I’m going to try and avoid doing for the entire period of my annual leave – just the first couple of days. I have been extremely tired, so a few sleep-ins will be helpful – for my health and well being you know. I’m sure you know what I’m talking about and agree with me entirely. I take your silence as tacit agreement. Thank you for that.

Myall Lakes National Park

Once I was up I thought I should do something – so the day wouldn’t be viewed as an entire waste. So a drive to Bulahdelah was on the cards via the Myall Lakes National Park and the Bombah Point Ferry. So that’s what I decided to do, after I thought through a few more possible options for…

View original post 313 more words

Holiday Planning: NSW Road Trip 2010


The planning for my holiday is now well and truly underway, with the holiday now being referred to as my ‘NSW Road Trip 2010.’ There is also a website address for viewing my itinerary and for following my progress. It has been a rushed process in the end, organising this road trip, so there will yet be some changes to the itinerary.

I am expecting changes in far western NSW due to road conditions, especially given recent weather conditions out that way, including the widespread rain and flooding that has taken place. Given I have only got a small rental for this trip, I am not really prepared to take the car onto certain roads (which I believe will be part of the rental agreement anyway).

At this stage I am expecting to miss Ivanhoe and head for Mildura instead. I also expect to miss Tibooburra in the far northwest corner of the state, as the Silver City Highway is largely dirt. With these probable changes to the itinerary, I will also miss driving through the Menindee Lakes area, which really was something I was hoping to see – another time perhaps.

On another ‘track,’ I found our that the hottest February temperature experienced in Ivanhoe was around 48 degrees Celsius. No, not the reason I am thinking of bypassing Ivanhoe – most centres out west have similar temperatures in February anyway.

The website:

http://www.kevinswilderness.com/NSW/nswRoadTrip2010.html