Feb 202014
 
20140214 Bristol Channel

20140214 Bristol Channel

Magnitude 4.1 earthquake in the Bristol Channel. Seismogram recorded at Keele University.

Probably associated with the Bristol Channel Fault System or one of the NW-SE strike slip faults that offset it.

Map from PESGB with approximate epicentre highlighted.

PESGB

[Update]
The Bristol Channel Fault System is a major fault zone along which it is thought that the Cornubian Peninsula docked against England and Wales in the Mid-Devonian. However, most UK earthquakes tend to be strike slip events on northerly trending faults due to the current stress regime in the UK (ridge-push from the North Atlantic from the NW + tail end of Alpine compression from the SE). A more likely candidate would be a fault parallel to the NW-SE trending Sticklepath Fault (going from Pembrokeshire and across Devon on the map) that offsets the Bristol Channel Fault System and on which there is evidence of significant strike slip movement during the Cenozoic.

More information from the British Geological Survey

As a comparison with ‘fracking’ events here is a useful chart. The Bristol Channel earthquake would be several centimetres slip on a 1 to 4 kilometre fault, a thousand times more powerful than the largest of the Blackpool events and about 30 million times for powerful than a typical ‘frack’ event.

FaultSizeFaultSlip

Aug 142013
 
20130813 Panama

Our ‘schools’ seismometer at Keele is now running the java version of amaseis software (called jAmaseis). The earthquake yesterday south of Panama (13/08/2013 M6.7) is our first real opportunity to play with the event viewer part of the software. The result is here…

20130813 Panama

First impressions are that the event window could be a bit larger to see more detail in the seismogram.

If you download jAmaseis from IRIS (www.iris.edu) you can now livestream Keele and other seismometers from around the world and pick and locate the events for yourself.

Jul 312013
 
John Milne 1850-1913 (Source: Wikimedia Commons / Tokyo University)

John Milne, the so called ‘father of modern seismology’ died 100 years ago today on July 31, 1913. There has been remarkably little fanfare (outside of the Isle of Wight) marking this centenary which is surprising for such a remarkable man. I can’t help thinking that if he had been a physicist or chemist (or even a palaeontologist or stratigrapher) there would be much more celebration.

John Milne 1850-1913 (Source: Wikimedia Commons / Tokyo University)

John Milne 1850-1913 (Source: Wikimedia Commons / Tokyo University)

Milne was born Liverpool on December 30, 1850, in his grandmother’s house but he soon moved to the family home in Rochdale, 147 Drake Street which he considered home.

147 Drake Street, Rochdale - the Milne family home. Note absence of Blue Plaque. Source: Google Streetview

147 Drake Street, Rochdale – the Milne family home. Note absence of Blue Plaque. Source: Google Streetview

The family later moved to Tunshill House on the outskirts of Rochdale, a building later demolished for the building of the M62 Motorway.

He studied Applied Sciences at King’s College London then Geology at the Royal School of Mines (then in Jermyn Street, London) and at the University of Freiburg, Germany. His early geological career involved coal exploration in Newfoundland (he was asked on a Friday “can you go on Tuesday?”) and he was employed by Dr. Charles Tilstone Beke who was searching for Mount Sinai. Whilst Beke’s search was ill-conceived, Milne profitably used the opportunity to study the geology of the Sinai Peninsula.

He then took up a three year post as Professor of Geology & Mining at Imperial College of Engineering Tokyo. He decided to travel to Japan from the UK overland. He largely travelled alone (because no one with sense would go with him) across Europe, Russia, Siberia, Mongolia & China by train, boat, horse & cart, camel, sled, and on foot – in winter! The journey of 13,000 km took 203 days (he was in no hurry) through the winter of 1875/6. He made geological notes all the way.

Milne's journey to Japan in the winter of 1875/6

Milne’s journey to Japan in the winter of 1875/6

On his first night in Tokyo felt an earthquake – triggering his life’s work in seismology. However, he was a polymath. He wrote a book on crystallography and being at a loss in the summers when not teaching, travelled Japan and the Kuril Islands studying its volcanoes, climbing over fifty of them. He is even credited in discovering a new volcano, Ebeko, in the Kuril Islands in 1878.

What changed things for Milne was the large Tokyo-Yokohama earthquake in 1880. Milne noticed the direction of pendulums set swaying gave the direction towards earthquake. He sent out questionnaires across Japan requesting the exact time, damage, fall direction of chimneys etc., effectively initiating the first macroseismic survey. However the results were inconclusive and Milne realised that the way to understand earthquakes was by better instrumentation. He set up the Seismological Society of Japan in 1880, the first such society in the world. 15 pendulums were installed to record quake movements across Japan – by the time he left Japan there were almost 1000.

He experimented with designs and created artificial earthquakes using explosives, once nearly getting killed by falling debris. With Thomas Gray (Professor of Telegraphic Engineering) he developed a three component seismograph recording on smoked paper (Gray-Milne seismograph) in 1881 and also pioneered the recording of electro-seismic phenomena, something that we are only returning to today. He researched and designed earthquake resistant buildings (including part of his house) with base isolation of the building on massive steel balls. In 1887 he was elected as a Fellow of the Royal Society.

In 1889 with John MacDonald of the Tokyo Locomotive Department he invented a compact, robust and portable three-component vibration recorder. The Milne-MacDonald vibration recorder was originally for vibrations of steam locomotives and since it could pick-up excessive vibrations from poor sections of track, identifying and repairing these made for safer railways both in Japan and in Britain.

He also influenced the BAAS (The British Association for the Advancement of Science) to set up the Seismological Investigation Committee in 1891 to investigate earthquake tremors that occurred in the British Isles.

In 1893 he developed his horizontal pendulum seismometer, the first properly capable of recording distant earthquakes. It should be remembered that at this time ‘modern’ study of earthquakes was just in its infancy. It was only in 1893 that Bunjiro Koto, a Japanese geologist and seismologist, after the Nobi 1891 earthquake, asserted that earthquakes were caused by faults not damage resulting from them.

In 1895 a fire destroyed his house, library and laboratory. He decided to leave Japan. He had married a Japanese girl, Tone, in 1881 but married her again at the British Consulate under British Law so that when he returned to the UK the marriage would be officially recognised. He arrived back in the UK in July 1895 and set up home and laboratory at Shide Hill House near Newport on the Isle of Wight. In 1896 a tsunami hit Japan and Milne investigated, writing a report on how the location of subsea faulting would affect global communications by cutting seabed cables. As a result, a global network of seismometers (Milne’s horizontal seismograph being the standard instrument) was set up, mainly in Commonwealth countries. Reports and seismograms came to Shide from all over the world and Milne painstakingly constructed earthquake catalogues “the Shide Circulars”.

Milne's World Earthquake Map for 1906

Milne’s World Earthquake Map for 1906

With John Johnson Shaw, Milne later developed the Milne-Shaw seismograph in 1913 which became the standard earthquake seismograph for many years. Milne died of Bright’s disease (kidney disease) July 31 1913 aged 62

Milne made our railways safer, invented the macroseismic survey, the modern seismometer, the first world-wide seismic network, the first proper global earthquake catalogue, and initiated the study of British earthquakes – yet the only memorial to him in the mainland UK is a pub restaurant, part of a Premier Inn, close to the site of the former Tunshill House outside Rochdale.

The John Milne Pub, Rochdale. Source: Google Streetview.

The John Milne Pub, Rochdale. Source: Google Streetview.

Sources:
Herbert-Gustar, L.K., Nott, P.A. (1980) John Milne: Father of Modern Seismology. Paul Norbury Publications Ltd, Kent. 188pp
International Seismological Centre – John Milne http://www.isc.ac.uk/about/history/milne/

The Isle of Wight Society is organising a series of events to mark Milne’s centenary http://www.isleofwightsociety.org.uk/jmilne.aspx
including an exhibition at Carisbrooke Castle Museum.