Tag Archives: geology

A geologist in the Italian earthquake

by Huw Goodall

Half awake, half asleep. The room is shaking. You realise you are not at home. You are in central Italy. Now the room is really shaking, you sprint over to hide under the desk as the floor moves under your feet, grabbing clothes as you go. The shaking continues, you put on the random assortment of clothes, pulling the bag you packed the night before, with the essentials to survive, close to you, wondering when the shaking will stop. Preparing mentally to be buried under the roof and hunker under the desk until the rescue team gets to you, you listen as the doors and windows rattle and bang. Then there is silence.

in_the_square_after_eq_HG.JPG
People gathered in Ascoli Piceno town square, not long after the earthquake. Copyright: Huw Goodall

Pulling your shoes on (why didn’t you untie them last night!) you run into the corridor, your colleagues are out there, everyone is unhurt. Down the gloomy hotel corridor you all hurry out into the square, where slowly but surely the population of Ascoli Piceno gathers in the beautiful early morning sun. After an hour or so delay, including dashing back into the ancient building to grab field kit, interviews with the BBC and a delayed breakfast, you escape from the medieval town towards the epicentre of the earthquake.

rocks_blocking_road_hg
Dodging boulders on the drive up towards the epicenter. Copyright: Huw Goodall

Driving up the winding mountain roads, dodging between boulders that have been dislodged by the shaking, your team of 4 make their way towards the centre of the earthquake. As you approach, the tiny villages that dot the route show increasing signs of damage. Then you see it. The rupture. This is where the earth has been cut by the quake. The work begins. High precision surveys are taken from this site, after a brief discussion it is decided to return to where you were working the previous day and see if the fault has moved in the earthquake there too.

fault_across_road
Our first encounter with the fault rupture, south of Mt Vettore. Copyright: Huw Goodall

This involves driving through the isolated town of Castellucio, a stunning hilltop village, famous for its lentils. As you drive up the hill, the residents are in the street. Your Italian is only good enough to order food, but you can tell they are scared, confused and don’t know why you are there. You are probably the second car at most that has passed this way since the earthquake that morning. The destruction is clear, walls collapsed a pancaked building along the road, other houses simply gone. There is a helicopter landing in the street. People are everywhere.

castelluccio_before_after
Before and after images of the destruction at Castelluccio.

Eventually the situation is explained in a hash of Italian and English and you are allowed to pass through, to continue to do your work as the people of the village continue to take stock. The next two weeks are non-stop field work, police checkpoints, late dinners and early starts. You measure how the fault has ruptured the surface, using a high-tech laser scanner, GPS, cameras and the good old fashioned ruler and notebook.

fault_scarp_hg_edited
The fault on Mt Vettore, the bad of pale rocks (red line) shows the amount of movement of the ground during the earthquake I experienced. Copyright: Huw Goodall

We spent the fortnight mapping new parts of the rupture as well as repeating measurements at some sites, to generate a picture of how the fault is moving in the days after the earthquake. This data set will be unlike any other in existence and hopefully will give us an insight into why earthquakes happen the way they do.


h-goodallHuw is a PhD student in the School of Earth and Environment at the University of Leeds. His work involves using precise chemical analysis of earthquake faults to understand how they have moved in the past.

Advertisements

Newspaper archive helps enrich UK landslide database

by Faith Taylor

“The past is the key to the future” – and so creating accurate and thorough records of past events is a common goal for many working in natural hazards. Recording the recent history of some natural hazards is relatively straightforward where automatic instrumentation can be widely used – e.g., using a network of seismometers to record earthquakes across the world. Yet, recording when and where landslides have occurred is a bit of a pain…

The mess of rocks, mud, water and debris left behind on the ground in a landslide is the outcome of a set of processes (e.g., rainfall, ground shaking, erosion). So, to find a landslide, one must actively search for it across a landscape – e.g., by traipsing about in the field, or searching through aerial imagery. It can take teams of geomorphologists literally years of work to create a thorough inventory of landslides from aerial images.

landslide_papers
Old newspapers contain a wealth of information on the location of landslides and their impact on communities.

One common way to supplement records of landslides is to use human records, such as newspapers, photographs and diaries. Two excellent examples are (i) Dave Petley’s global fatal landslide database, which uses online news to record deaths caused by landslides, and (ii) the Italian AVI project has records of landslides going back hundreds of years from newspapers.

Yet when searching the literature, we noticed two things – firstly, people aren’t doing this for Great Britain and secondly, people weren’t really talking about how they searched the newspaper archives. I was lucky enough to receive a NERC-EPSRC internship to work with the British Geological Survey on searching the Nexis UK Digital Archive of regional newspapers to try and find articles about landslides.

The first step was experimenting to create a systematic search strategy to be sure that we were picking up as many articles about landslides, and as few articles about things like “landslide victories” as possible. Once this was settled, I applied our search to the Nexis UK archive (thank goodness this is digital and I didn’t have to flick through dusty old newspapers!) and started reading through the thousands of articles returned.

When I found an article about a landslide, I would try to extract as much information as possible, such as the timing, location, size and impact. I would then compare this to what was already in the BGS National Landslide Database to see if we were adding in more detail. To our surprise, this method was really effective and we increased the number of records in the database between 40% – 122% depending on the year examined. These additional records help us to better understand when, where and why landslides occur in Great Britain, and what kinds of impact they can cause.

Our Geomorphology Article is Open Access and available online at: http://www.sciencedirect.com/science/article/pii/S0169555X15300039

——————————————————————————————————-

Faith Taylor is a postdoctoral research scientist at Kings College London. Find out more about her work here. You can follow her on twitter @faithatron

The public misunderstanding of the geological subsurface

This is really really important and relevant to all areas of natural and environmental hazards.

Professor Iain Stewart goes over some of the problems in science communication and the public misunderstanding of the geological subsurface.

“We need to find a way to connect people to the subsurface.”
Professor Iain Stewart

Balancing rocks and the earthquake detectives

Scientists have solved a mystery as to why precariously balanced rocks near the San Andreas Fault have never been toppled over by earthquakes.

During large earthquakes shaking of the ground causes unstable structures, both natural and man-made, to collapse in a wide region around the source of the quake. This high shaking zone can be anything from a few kilometres to hundreds of kilometres depending on the size of the earthquake.

Nick Hinze / Nevada Bureau of Mines & Geology
Nick Hinze / Nevada Bureau of Mines & Geology

It’s long been an intriguing mystery as to why many so called “precariously balanced rocks” are found in close proximity to one of the most active earthquake generating structures in the United States: the San Andreas Fault. Some of these rocks have been balanced for thousands of years. During which there might have 50 -100 earthquakes in the area.

A decade long study by US scientists, measuring and cataloguing balancing rocks along with computer modelling reveal that interactions between the San Andreas Fault and the neighbouring San Jacinto Fault may be the answer to the mystery.

The researchers believe that precariously balanced rocks have survived because interaction between the two faults has weakened earthquake ground shaking near them.

“These faults influence each other, and it looks like sometimes they have probably ruptured together in the past,” said lead author Lisa Grant Ludwig. “We can’t say so for sure, but that’s what our data point toward, and it’s an important possibility that we should think about in doing our earthquake planning.”

The scientists have realised that these rocks could provide a check for seismic hazard maps, and give long-term indications of ground shaking.

“”They are kind of natural seismoscopes – but you have to read them indirectly.”

More information:
[1] Press release – http://news.uci.edu/press-releases/precariously-balanced-rocks-provide-clues-for-unearthing-underground-fault-connections
[2] Journal article – http://srl.geoscienceworld.org/content/early/2015/07/31/0220140239.extract