The Earthquake Detective: Robert Mallett


The first photographs ever taken of the aftermath of an earthquake were taken of the Great Neopolitan Quake of 1857, which destroyed the village of Pertosa, pictured here, and many other towns and villages in southern Italy. The pictures were taken by a Frenchman called Grellier, and commissioned by Irish scientist and Dubliner Robert Mallett who was the first to determine what caused earthquakes such as this one [Credit: Dublin Institute for Advanced Studies].

Listen: Interview on Robert Mallett with Irish geophysicist, Tom Blake

First broadcast on 103.2 Dublin City FM 10/12/2009

——————————————————————————-

The science of seismology, which studies the power and energy unleashed by earthquakes, began life on a south Dublin beach in 1849 with an ingenious experiment carried out by one of Ireland’s greatest scientists. That scientist was Robert Mallett – a Dubliner widely recognized as the ‘father of seismology’. Widely recognized that is, outside Ireland, where he remains largely an unknown figure outside the scientific community.

A true blue Dub you might say, Robert Mallett was born on Capel Street, on the banks of the Liffey, on the 3rd June 1810. His father owned a successful iron foundry business. The legacy of this foundry’s success can still be seen today, on the iron railings around Trinity College, which are inscribed with the name R&J Mallett.

From an incredibly early age, Robert was interested in science, and in particular chemistry. From the age of perhaps two, or three, he had his own small laboratory set up in the family house, where he played with chemicals. Such was Robert’s enthusiasm for spending time in the lab, the story goes, that his parents used to lock him out of the lab in order to punish him for some misdeed.

Later, in his teenage years, he went down the road to TCD to study science. The science course at TCD at that time – the early part of the 19th century – was more like what we would recognise as engineering today – very technical. After his studies were complete he went back to work in the family business. He continued to have a fascination with all things science, and began to conduct experiments on how sound or energy moved through sand and rock.

KILLINEY

In October 1849, aged 39, Robert, and his son John, who was a chemistry student at TCD, decided to carry out a remarkable experiment on Killiney Beach. They wanted to prove that energy moved through sand and rock in waves that could be measured, and they designed a ‘controlled’ experiment to prove this was so.

The two Malletts buried a keg of gunpowder in the ground, and detonated it. They measured the energy wave that traveled through the sand at a distance of half a mile away, with a seismoscope. The experiment worked, and a seismic reading was generated that showed clearly, energy moved through sand in waves.

Robert also worked closely with William Rowan Hamilton, another great Irish scientist and mathematician. William had suggested to Robert that he might apply the laws of physics, as they apply to light, in order to describe how the energy generated by the explosion would pass through sand and rock (for the rock measurements he set up a seismoscope on nearby rocky Dalkey Island, rather than the sandy beach). Robert took William’s advice and Robert’s report on his experiment became the foundation of modern seismology.

ITALY

Robert is not well known in Ireland, except amongst the small community of geologists and earth scientists that would appreciate his importance in the advancement of our understanding of earthquakes.

However, in southern Italy Robert is well known, due to his role in studying the after affects of the ‘Great Neapolitan Earthquake of 1857′. This earthquake – which was the third biggest in recorded history at the time – struck in deadly fashion on the 16th December, and killed in the region of 20,000 people.

Robert reacted quickly and wanted to go to the earthquake zone and record the devastation, using the new technology of photography. Two powerful friends, Charles Lyle, a famous English geologist, and Charles Darwin, helped Robert to get a grant from the Royal Society to travel to Italy and carry out this work.

Robert arrived in Italy and worked right through Christmas and into the New Year, diligently recording the devastation along with a French photographer. This was the first time ever that photography had been used to take images of the after affects of an earthquake. It was a revolutionary approach at the time.

Robert’s report entitled ‘Great Neapolitan Earthquake of 1857: The First Principles of Observational Seismology’ was published by the Royal Society in 1862. It remains as ‘seminal research’ into seismic hazard and seismic risk, said Tom Blake, experimental officer in the geophysics section of the Dublin Institute for Advanced Studies (DIAS).

The bicentenary of the birth of Robert Mallett was held in 2010 and the DIAS and the Royal Dublin Society had joint celebrations. This was done, said Tom Blake at the time, “so that, at least, once and for all, Irish people will understand, and know, that the father of controlled-source seismology is an Irishman – Robert Mallett”.

SEISMIC SCIENTISTS

In 132 AD, in China, a man called Zhang Heng, invented the world’s first seismometer – an instrument capable of measuring ground movements due to earthquakes. The machine Zhang invented enabled him to determine the direction and occurrence of the epicenter of an earthquake. For example, his device could pinpoint an earthquake occurring at a location 400 miles away, long before horse-bound messengers could bring the Emperor the bad news. This enabled the Emperor to quickly dispatch help to the afflicted area.

The west was far behind China in seismic studies. As late as 1755, more than 1,600 years after China had invented the first seismometer, people believed that the Great Lisbon Earthquake of that year, which killed 70,000 with an accompanying tsunami, was God’s punishment for the sins of mankind.

Not everyone in the west believed in the ‘God’ explanation for earthquakes in the 18th century. One of those was John Mitchell, a clergyman, and academic at Cambridge University. Mitchell proposed that earthquakes caused by energy waves originated below ground. At the time, his theory was largely ignored.

In 1795, Ascanio Filomarino devised a seismograph similar to the one Zhang had invented centuries before. It had a part that would stay stationary while the rest of the instrument would shake when an earthquake was occurring, and ring bells and set off a clock. Poor Ascanio was murdered on Mt Vesuvius by an angry mob that didn’t like his work. They also burned his workshop and destroyed his seismograph.

Another early ‘seismograph’ was developed by Luigi Palmieri, in 1855. Palmieri was the director of an observatory near Vesuvius. An instrument, designed by Palmieri, could measure small tremblings in the ground around Vesuvius, and recorded such movements on a paper strip – like later seismographs.

The big contribution of Robert Mallett to this emerging field came in 1857 when he examined the damage caused by the earthquake in Italy of that year. He generated isoseismal maps, which displayed contours of damage intensity. He also published a world map that revealed the clustering of earthquake incidences in specific locations around the planet. Thus, Mallett, was the first to see the ‘big picture’ with regard to earthquakes.

First published in the September-October 2009 edition of Science Spin

How Irish Scientists Changed the World, by Seán Duke, is due for publication by Londubh Books in Spring 2012.

About these ads

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 782 other followers

%d bloggers like this: