Geologists in the land of the Kangaroo

Terra Australis - the southern continent had been “discovered” by Europeans already in 1606, but only in 1642 the size of the new “island” becomes clear and the first geological observations  were made only in the early 19th century.

October 1800 two ships – the “Geographe” and the “Naturaliste” – set sail from the harbor of Le Havre, France. Under the command of Captain Nicolas Baudin (1754-1803) geographers, astronomers, artists, naturalists, zoologists, botanists, and 2 mineralogists – Louis Depuch (1774-1803) and Charles Bailly (1777-1844) – were instructed to explore, map and eventually claim for France new territories of this new world. In the last moment also the young zoologist, and trained paleontologist, Francois Auguste Peron (1775-1810) joined the expedition.

The geological observations made by Depuch (died during the expedition) are known from various reports send to Baudin. Bailly will publish some notes after his return to France and Peron included his research in the official report of the expedition.

In May 27, 1801 the bare land of Cape Leeuwin was in sight and the naturalists went on land along the Wonnerup Inlet, where they collected the first specimens of Australian animals, plants and rocks.

 

Fig.1. The “Baudin” – expedition, route drawn on Louis de Freycinet´s (1779-1842) “Carte générale de la Nouvelle Hollande”, published in 1811 as part of the results of the 1800-1804 expedition.

A storm forced the men to remain on land for several days and one man died during a failed attempt to reach the ships (during the entire expedition 32 men died, 13% of the crew, a surprising low percentage considering the period). The storm separated the two ships, the “Naturaliste” proceeded to the island of Timor, a Dutch colony at the time, where the crew fell ill with Malaria and other tropical diseases. The “Geographe” approached in November 1801 the island of Tasmania, where the expedition will stay for three months.
April 1802 the “Geographe” meet the British vessel “Investigator“. The expedition of the “Investigator” will map large parts of South-Australia and prove that Australia is one large continent, not two islands separated by a sea strait, as some geographers assumed. This was a disappointing discovery for captain Baudin, as there was no apparent geographic separation between the territories already claimed by British explorers, the entire continent had to be considered of British domain.

Captain Baudin, the crew and the naturalists could now only hope to gain some fame with the scientific results of the expedition...

The geologists Depuch and Bailly used a rock classification scheme, developed by the famous French geologist Déodat de Dolomieu, with four categories. They recognized primary rocks, such as granite; secondary rocks, such as stratified sandstone and limestone; alluvium (recent deposits) and volcanic rocks, such as basalt. The presence of these rocks in Australia was an important discovery, it proved that the classification scheme developed in Europe could be applied worldwide.

 

Fig.2. Charles-Alexandre Lesueur´s and Nicolas-Martin Petit´s depiction of Van-Diemen´s-Land for the “Voyage de decouvertes aux Terres Australes“. The two young men – unskilled workers at the beginning of the expedition -  were invited by Baudin to illustrate the logbook  -  both will become the most skilled artists for animal- and plantlife of the time. The granitic rocks found on the island of Tasmania convinced Peron and the other geologists that the most ancient – the primary – rock was Granite, forming the basement of all continents.

Paleontologist Peron noted along the west coast of Australia horizontal sand- and limestone layers (the Tamala-Limestone) and concluded, based on similarities to recent sediments, that these layers were deposited along an ancient beach, implying substantial variations in the sea level during geologic time:

“One of the greatest achievements of modern geology research and also one of its most indisputable, is the certain knowledge that, in the past, the level of the sea was higher than at the present time. At almost all places in the old and the new world is the proof of this phenomenon as numerous as it is evident. Only in les Terres australes was this still to be ascertained as, by virtue of its immense areal extent, it could have proved to be an important exception to the universality of the former domination of the ocean over the land.” 

(PERON & FREYCINET 1816)

Unfortunately the return to France will be disappointing for Peron. Captain Baudin dies on the island of Timor and French authorities will show little interest in the 220.000 samples of animals, plants and rocks, the 73 living animals, 3 kangaroos, 2 emus and 3 wombats brought back to Europe.

Peron publish his report “Voyage de decouvertes aux Terres Australes” only in  1807, after a long struggle for money and dies just three years later, before the completion of the second volume. However the sea shells collected during the expedition will be studied by an important French naturalist – Jean-Baptiste de Lamarck. In 1804 Lamarck publishes his theory about the transmutation of species, based in part of the observation that the fossil shells found in the sediments of France are similar, but not identical, to shells of living molluscs collected in Australia.

 

Fig.3. Peron discovers on the shores of Tasmania a living clam with a peculiar triangular shape – Trigonia antarctica – a genus of bivalve known only from fossils found in the sediments of the basin of Paris. He notes the similarities of this living specimen with fossil specimens – an important step to consider a relationship between fossil and extant species. Image of Trigonia sp. from Cretaceous sediments of Bavaria.

Unfortunately for Lamarck – and the naturalists of the Baudin expedition – he mixed his careful observations with wild speculations. Lamarck noted variations of organisms in time, however he could not explain why such variations occur or why certain organisms went extinct or survived – apart invoking a final cause and implying a sort of supernatural scheme. Geologist Charles Darwin will later regard Lamarck’s work as “useless“...

Fig.4. Geological map by Jules Grange, published in 1850, surprisingly little was known of the geology of Australia until the 20th century.

Bibliography:

GLAUBRECHT, M. & MERMET, G. (2007): Josephines Emu oder Die Geschichte einer vergessenen Expedition. GEO Nr.6/2007: 98-122
MAYER, W. (2008): Early geological investigations of the Pleistocene Tamala Limestone, Western Australia. from GRAPES, R.H.; OLDROYD, D. & GRIGELIS, A. (eds) History of Geomorphology and Quaternary Geology. Geological Society, London, Special Publications 301: 279-293
MAYER, W. (2009): The Geological Work of the Baudin Expedition in Australia (1801-1803): The Mineralogists, the Discoveries and the Legacy. Earth Sciences History Vol.28 (2): 293-324
RUDWICK, M.J.S. (2005): Bursting the limits of time – The reconstruction of Geohistory in the Age of Revolution. The University of Chicago Press, Chicago, London: 708

8, July 1836: Darwin on St Helena

The HMS Beagle, with on board the amateur naturalist Charles Darwin, arrived at the remote island of St Helena on July 8, 1836, where it stayed until noon of July 14, afterwards proceeding its journey back to the United Kingdom and setting sails to the nearby island of Ascension.
Darwin used these five days to explore the geology of the island and hired an elderly man as a guide. Since Van Diemen´s Land Darwin's written notes and observations had become more hasty and fragmentary - as a combination of the short stops by the Beagle on the single islands and maybe a bit of homesickness, nevertheless Darwin dedicated later one of his notebooks, written down in September to December 1938, to the island, the "St Helena Model", where he on 15 pages noted observations and thoughts on the general island geology (and also troubles with the laundry).
As already on the island of St. Jago Darwin noted various geological evidence that the island had risen from the sea in an outcrop of basaltic rocks:

"The successive sheets are either closely united together, or are separated from each other by beds of scoriaceous rock and of laminate tuff, frequently containing well rounded fragments. The interstices of these beds are filled with gypsum and salt; the gypsum also, sometimes occurring in thin layers. From the large quantity of these two substances, from the presence of rounded pebbles in the tuff, and from the abundant amygdaloids, I cannot doubt that these basal volcanic strata flowed beneath the sea."
DARWIN (1844) "Geological Observations on the volcanic islands and parts of South America visited during the Voyage of H.M.S. "Beagle"." 75-76

Fig.1. A section trough the coastline of St Helena by the hands of Charles Darwin (dated 15 September 1838), from CHANCELLOR 1990.

At the time the origin of volcanoes as mountains was under scrutiny, one model - proposed by the eminent German geologist Leopold von Buch (1774-1835) - stated that volcanoes form like a bubble: first geologic forces upraise the ground and form the mountain, the summit collapses, forming the steep crater walls, finally the magma can spout trough the surface, causing an eruption. Lava flows or ash layers where therefore a secondary feature of volcanoes, not the "construction material" of the volcanic complex. This "crater of elevation" hypothesis was very popular at the time and supported by most European geologists. Two French geologists, Armand Dufresnoy (1792-1857) and Léonce Elie de Beaumont (1798-1874), tried even to prove mathematically that continuous lava flows can form only on surfaces with an inclination less than 6°, according to their calculations on steeper surface a flow start to disintegrate, and as most observed lava flows were however steeper, this observations could only be explained by the surface of the volcano steepen over time.

Fig.2. Topographic map of the Canary Island published by von Buch in 1814 in his book "Description physique des lles Canaries, suivie dúne indication des principaux volcans du globe." Von Buch assumed that the radial valleys, descending from the central summit, are fissures caused by the inflation and uprising mountain - in fact these valleys are formed by the erosion of the volcanic rocks.

Darwin did not share entirely this vision of uprising volcanoes; in part the model proposed very fast rates of elevation and Darwin was more inclined to follow the gradual geology as proposed by Charles Lyell - Lyell himself refused the "crater of elevation" hypothesis outright.
Darwin addressed the problem only superficially: he used the observations on St Helena to formulate an intermediate hypothesis, volcanoes rise by slow, gradual and episodic events, he also suggested that more research was necessary to map and determinate the inclination of lava flows.

In 1850 Lyell demonstrated on a lava flow of Mount Etna that the lava solidified on a slope inclined by 35° - the "crater of elevation" hypothesis had lost one of its most important arguments and Darwin left behind the hypothesis of inflating volcanoes.

Bibliography:

CHANCELLOR, G.R. (1990): Charles Darwin's St Helena Model Notebook. Bull. Br .Mus. Nat. Hist. 18(2): 203-228
HERBERT, S. (2005): Charles Darwin, Geologist. Cornell University Press: 485
KRAFFT, M. (1993): I vulcani - il fuoco della terra. Universale Electa-Gallimard: 191

The Geisha and the Tsunami

More than a month has passed since the earthquake and the Tsunami that devastated the coast of north-eastern Honshu.
After the first shock people begin to ask if the extent of destruction and number of victims (more than 14.000 confirmed dead and 12.000 people missing) could be predicted. There are various hinds that can help to produce a risk map - there is geological evidence like fossil Tsunami deposits, there are in prehistoric time maybe myths and legends surviving in oral traditions, there are in historic time written stories in chronicles, scientific observations and measurements in charts, there are monuments, but there are also the eyewitnesses' reports of survivors.

In various newspapers and online media the accounts of many survivors of the last Tohoku tsunami were reported, the story of the geisha Tsuyako Ito is remarkable because it provides us with a scale how often Japan was hit by such disasters - even in the span of a single human life.
With her 84 years she experienced three tsunamis who hit the city of Kamaishi and as a girl she had listened to her grandmother's tales of the great 1896 tsunami.

"My grandmother said that a tsunami is like a wide-open mouth that swallows everything in its path, so that victory comes to those who run away as fast as possible."

The German newspaper "stern" published this old photography of a performance by Tsuyako Ito, she lost everything in the devastating Tsunami except her memories - and she promised not to surrender.

Her mother carried her on her back to safety at the time of Ito's first tsunami in 1933. This time, her fourth and "most frightening" tsunami, she was saved by an admirer who carried Ito on his back to higher ground.

The warnings of such experiences unfortunately last only a short time, according to the Japanese Yotaru Hatamura who studied ancient traditions about Tsunamis in Japan:

"It takes about three generations for people to forget. Those that experience the disaster themselves pass it to their children and their grandchildren, but then the memory fades," he said.

After the earthquake that devastated Tokyo in 1923 and San Francisco in 1906 the opportunity to rebuild the cities following antiseismic principles was abandoned to provide a fast reconstruction.

We shouldn´t ignore or forget...

Online Resources:

ONISHI, N. (08.04.2011): Geisha survives with help from an admirer - Guardian of a local culture has lived through four tsunamis. (Accessed on 25.04.2011)

27 March, 1964: The Alaska Earthquake

“One day earthquake and thunder decided to explore the world, but doing so they reached only a desolate and dry plateau. Earthquake noted that the land was located much too high in the sky for humans “They will have no food, if there is no place for the creatures of the sea to live in!” Earthquake begun to shake, stronger and stronger, until the earth finally collapsed and the sea inundated the land. Earthquake was satisfied “From here, they will obtain what they need to live, where prairie has become water…. This is what brings to the people life.” Thunder acknowledged what earthquake had done “It is true. So they will survive!” and so they went further north and together they lowered the land and created the western coast.”
The creation of the world according to a legend of the Yurok people (Cascade Range)

In the late afternoon of March 27, 1964 Alaska was shaken for five minutes by one of the strongest earthquakes ever to be recorded in modern times, with a magnitude of 8.3 – 9.2 after Richter (the earthquake was so strong that no seismometer in the affected area recorded it correctly).
The earthquake displaced almost the entire southern coast of Alaska along the Prince William Sound, some areas were raised by 9 meters (30 feet) above the sea level, other dropped below sea level and became inundated later by the sea (maybe the Yurok myth is based on the observation of such a similar environmental change after an earthquake in prehistoric times along the western coast of the U.S.).

The earthquake caused heavy damage on 75% of buildings and infrastructure in the affected area, most in the city of Anchorage, 131 people were killed.
Large fissures opened in the ground when the groundwater liquefied the soil and more than 2.000 landslides and avalanches occurred across south-central Alaska. Buildings in Seattle (Washington) begun to swing by the approaching seismic wave and the ground was measurable deformed even in Florida.

Fig.1. Aerial photographs of destructive landslides and damage in Anchorage, Photo by A. Grantz / image in public domain from the U.S.G.S. Photographic Library.

In some lakes in Alaska the movement of the water catapulted chunks of ice onto the land, causing damage on the surrounding trees up to 9 meters (30 feet) above ground. Unusual water movements, attributed cautiously to the earthquake, were observed in South Dakota and apparently even in Puerto Rico and Australia.
Most remarkable was the generated tsunami, waves higher than usual were observed even along the Japanese coast. The seaport of Valdez was destroyed by a 30 meter high tsunami, 32 people died there. For hours after the earthquake the sea was tumultuous and in the evening with the high tide the reflected waves of the first tsunami inundated the surviving area of the city of Valdez.
Six hours after the earthquake the tsunami reached the coasts of Vancouver Island, one hour later the coast of Oregon and the wave caused damage even in Crescent City and Los Angeles (California). 

Many of these phenomena were studied for the very first time by scientists – only two hours after the earthquake the first geologists arrived to Anchorage.

Fig.2. Alaska Earthquake March 27, 1964. Rockslide avalanche on Sherman Glacier. The source was from the area marked by the fresh scar on Shattered Peak (top center image). The debris displays flowlines and terminal digitate lobes. No marginal dust layer is present. The steep margin, about 20 meters above the clear ice, is due to more rapid melting of the exposed glacier than the ice protected by the debris. Photo by A. Post, August 25, 1965 / Geological Survey.

Bibliography:

Committee on the Alaska Earthquake of the Division of Earth Sciences National Research Council (1968): The Great Alaska Earthquake of 1964. National Academy of Sciences, Washington: 473
GATES, A.E. & RITCHIE, D. (2007): Encyclopedia of earthquakes and Volcanoes. Facts on file science library. 3th ed. New York: 346
WALKER, B. (1982): Earthquake. Planet Earth. Time Life Books: 154

Online Resources:

GATES (2007): U.S.G.S. (21.10.2009): Historic Earthquakes - Prince William Sound, Alaska 1964.

Tsunamis in the geological record

Tsunami deposits are well documented in the Holocene and the Pleistocene, in part by the good accessibility in outcrops to rocks of these epochs or when historic records help to identify areas subjected to tsunamis.

Modern databases list more than 2.000 tsunami events for the lat 4.000 years, most of them recorded in documents and chronologies and others inferred by their geological evidence.
It seems also possible that tsunamis in historic times (after 1700) have found place in myths and oral tradition of the local Indian tribes of the Cascade Range. Based on these stories geologists tried to establish a chronology of events, backed by geological evidence.

Fig.1. Temporal distribution of 2341 tsunami events listed in the database of the National Geophysical Data Center, USA. The database contains the events of the past 4000 years until 2001 AD, from SCHEFFERS & KELLETAT 2003.

However such a database has to be very incomplete, tsunami without greater damage or loss of life are likely to be underrepresented in historic documents, tsunamis with disastrous effects can in contrary became overemphasized and tsunamis occurring in uninhabited regions will not even be noted by humans. With the age of colonization and exploration the known and inhabited zones grow rapidly, and so also the record of large, destructive tsunamis apparently experienced a mayor increase.
However it can be assumed that the actual number, frequency and power of tsunami in such a compilation are still inaccurate and probably underestimated in the past and emphasized in the present the occurrence of strong tsunamis.
In the geologic record examples of ancient tsunamis are however quite rare. The coastal environment, like flood plains or the estuary of a river, are subject to continues reworking, erosion and deposition, a single event like a tsunami can got destroyed even before it's deposits or traces can became fossilized.
Also in such a complex environment single events tend to became homogenized and amalgamated with the "background" sedimentation, like deposits of the tides or storm events.

In theory a tsunami can produce various geologic evidences in four phases: it can both deposit sediments and erode them during generation, propagation, run up on land and backwash current. The sedimentologic record of the run up by a tsunami on land is well described by this post at "Trough The Sandglass", especially sand layers, and it´s environmental effects at "paleoseismicity" - however tsunamis can transport and deposits giant boulders (like reef debris thrown on land), these boulders are unlikely to be reworked by normal processes of a coastal environment and have a great potential to become fossilized.
Liquefaction phenomena like sand dikes and intrusion during the earthquake are preserved in the sediments underlying the soil and tsunami deposits.

Fig.2.Worldwide published distribution of coastal boulders thrown on land as evidence for tsunamis. Historical tsunami and storm wave boulders were defined here as those purporting to show clear depositional evidence based on historical descriptions, direct observations, and analyses of aerial photographs during the historical age (from GOTO et al.2010).

There is also indirect biological evidence to infer the occurrence of a tsunami.

A strong earthquake can cause a displacement of great parts of a coastal area and the land can become inundated by the sea. The salt water soon will kill trees and plants growing on this land. Because dead trees will survive for quite a while as "Ghost forests" the tree stumps can became buried in the sediments of the tidal flat. After the displacement the land can rise upward by the continuing tectonic movements and again became dry.
These changes can be observed in the stratigraphic succession: layers of peat or soil with tree stumps will change suddenly to sand and silt layers deposited by the tsunami and the tides. The plant remains can be dated by the radiocarbon method and are used to produce a chronology of the changes.

Fig.3. Summer in the ghost forest in Alaska and the remains of the town of Portage after the earthquake of 1964 and in the year 1998. In the background of the old photo spruce trees are dying and the high tide covers recently subsided land. In the modern photo still few trunks are standing and shrubs cover the land rebuilt by tidal silt (after BOLT 1995 and ATWATER et al. 2005).
The 1964 Alaska earthquake was a megathrust earthquake that began at 5:36 P.M. on Good Friday, March 27,.1964. Across south-central Alaska, ground fissures, collapsing buildings, and tsunamis resulting from the earthquake caused about 131 deaths.

The remains of the trees provide even a more accurate chronology: The sudden occurrence of the event is proved by the tree rings, a gradual subsidence of the land would produce a different pattern in the rings that the sudden interruption often observed in cedar trees along the North American coast.

Bibliography:

ATWATER, B.F.; SATOKO, M.-R.; KENJI, S.; YOSHINOBU, T.; KAZUE, U. YAMAGUCHI, D.K. (2005): The Orphan Tsunami of 1700 Japanese Clues to a Parent Earthquake in North America. U.S.G.S. - University of Washington Press: 144
BOLT, B.A. (1995): Erdbeben - Schlüssel zur Geodynamik. Spektrum Akademischer Verlag, Berlin: 219
DAWSON, A.G. & STEWART, I. (2007): Tsunami deposits in the geological record. Sedimentary Geology 200: 166-183
GOTO, K.; KAWANA, T. & INAMURA, F. (2010): Historical and geological evidence of boulders deposited by tsunamis, southern Ryukyu Islands, Japan. Earth-Science Reviews 102: 77-99
SCHEFFERS, A. & KELLETAT, D. (2003): Sedimentologic and geomorphologic tsunami imprints worldwide-a review. Earth-Science Reviews 63: 83-92

Historic tsunamis in Japan

Fig.1. Kanagawa Oki Uranami - "The Hollow of the Deep-Sea Wave off Kanagawa", coloured woodcut from the collection of "Thirty-Six Views of Fuji" (1831) by Japanese artist Katsushika Hokusai. The contrast between the various elements reflects the harmonic order between Ying and Yang and the necessity of solidarity of men in case of natural disasters.

The destructive power of water from the sea - Ying- contrasts with the calmness of the fishermen - Yang- the symmetric symbol is also formed by the wave and the sky. The similar colour of the volcano in the background and the wave emphasise the harmony between mountain (symbol for the body) and wave (symbol for the soul).
Many books describe this wave as a tsunami, but it's shape, characterized by a deep leading through and a very peaked crest, reveals it's origin from the wind. Only some tsunamis resemble such a wave and only near the shore.

The words "tsu-nami" in Japanese means "wave in the harbour", the name derives from the experience of fishermen that only when they returned from the sea into the supposed secure harbour they discovered the terrible destruction that these waves can cause on the shore. Tsunamis are generated by the rapid dislocation of large quantities of water by displacement of the seafloor triggered by earthquakes or landslides, also by explosions caused by volcanic eruption or meteoric impacts. The Pacific Ocean is surrounded by tectonic active borders of the lithospheric plates; nearly 53% of tsunamis worldwide occur here and 82% of them are caused by earthquakes.

Fig.2. Location of tsunami in the Pacific Ocean region: A) Location of 1.274 tsunami since 47 BC. Size of circle increases proportional to number of events per degree square of latitude and longitude. B) Source of significant distant tsunami - tsunamis generated at the coast of Japan can have effects on the coasts of the American continents and vice versa. Size of circle increases proportional to area affected and magnitude of the event, after BRYANT 2008. Note however that the diagram is biased against well studied coast regions (like U.S.A.) or areas with long written records (Japan).

Recognized Tsunamis sediments in Japan go back nearly for 5.000 years, historic records span for nearly 1.300 years, however the most detailed and precise accounts cover mostly the recent period.

An earthquake offshore the north-eastern coast generated a large-scale tsunami on July 13. in 869, we read in the Nihon Sandai Jitsuroku - the "The True History of Three Reigns of Japan" compiled in the year 901:

"Some time after severe seismic shocks, a gigantic wave [tsunami] reached the coast and invaded entire Sendai plain. Rising seawater flooded an old castle town [Tagajo], causing the loss of 1000 lives."
Inscriptions on up to 600 years old stone marker located near the coastal city of Kesennuma warn descendants:
"Always be prepared for unexpected tsunamis. Choose life over your possessions and valuables."
"If an earthquake comes, beware of tsunamis."
"High dwellings are the peace and harmony of our descendants, remember the calamity of the great tsunamis. Do not build any homes below this point."

In 1596 an earthquake offshore reportedly generated a tsunami that destroyed the island of Uryu-Jima completely and caused more than 4.000 deaths.
An official diary about the life and work of the Japanese warlord Tokugawa Ieyasu in his residence city of Sumpu from 1612 contains what is probably the earliest example of the written word of "tsu-nami". The text contains eyewitness-reports of a tsunami that hit north-eastern Honshu, killing thousands of people on December 2. 1611.

On 26. January 1700 contemporary chronicles describe a surprising tsunami, which caused minor havoc, but was not preceded by an earthquake (that earthquakes can be followed by a tsunami was already a well known fact). Research 300 years later revealed that this "orphan tsunami" was generated by an estimated magnitude 9 earthquake offshore the North American coast.

Possibly one of the largest tsunamis recorded in the history of Japan followed a strong earthquake in 1737. Information is scarce and written records are based mostly on rumours: according to these a 64meter (!) high wave devastated the island of Yezo (modern Hokkaido) and destroyed the coastal city of Kamaishi, thousands of people died.

On June 15. 1896 many villages along the coast of Sanriku were celebrating the return of the soldiers from the war against China, when an earthquake of magnitude 8.5 occurred nearly 145 kilometres offshore of Honshu.
The direct effects of the five minutes long quake were of minor entity, the epicentre was distant enough to reduce catastrophic movements on the main island and earthquakes were nothing unusual in this region.
However 35 minutes after the earthquake the most devastating tsunami experienced until then in modern Japan hit the coast, one of the subsequent waves reached a height of over 30-38 meters. 26.000-27.122 people were killed and 9.000 buildings destroyed, the effects of the Tsunami were observed over the entire Pacific, in Hawaii some houses were swept away and a three meter high wave reached the coast of California.
Fig.3. Drawing by Walter Molino, published in the Italian newspaper "La Domenica del Corriere" January 5, 1947, of a tsunami, probably the tsunami of the Great Tokyo Earthquake of the 1. September 1923. The devastation of the earthquake was caused mainly by the subsequent fire, but it triggered also a 11m high wave - estimated 90.000-130.000 people were killed.

In 1933 another very strong tsunami hit the coast of Sanriku. The earthquake of magnitude 8.4 occurred on March 3. 1933, this time also the quake caused heavy damage and landslides, it was then followed by a 21m high tsunami; In sum more than 6.000 people died.
The dead toll was significantly lesser then in previous events, in the years after the tsunami of 1896 authorities had invested in catastrophe mitigation, escape routes were build and the coast reinforced by special constructions (4m high walls and artificial barriers) and planted trees. Most effort was put into education; booklets warned of the consequences of earthquakes in the sea and explained the signs of danger of a incoming tsunami: a tsunami can be preceded by a loud noise like a thunder, the most important warning sign is however the temporally retreat of the sea before the first wave.

In May 1960 a tsunami generated by an earthquake off the coast of Chile reached the coastline of Hokkaido, causing havoc on the island of Okushiri, 142 people were killed.Okushiri was hit again in more recent years. July 12. 1993 an earthquake of magnitude 7.8 caused an 6-10m high tsunami that hit the small island to the west of Hokkaido (in nearly the same region an earthquake on August 29. 1741 produced a tsunami with a maximum run-up of 90m along the adiacent coast). From 680 buildings in the city of Aonae 550 were destroyed or damaged, more than 200 people were killed.

Tab.1. List of the deadliest tsunamis in Japan's history with date/year, affected region and estimated death toll, adapted from KOZAK & CERMAK 2010.

28.10.1707- Tokaido-Nankaido 30.000
1826- Not specified 27.000
20.09.1498- Nankaido 26.000
27.05.1293- Sagami Bay 23.024
15.06.1896- Sanriku, a wave generated by the Riku-Ugo earthquake killed 20.000-26.000 people
21.05.1792- Southwest Kyushu 14.500-15.030 (tsunami triggered by the eruption of the Unzen)
24.04.1771- Ryukyu 13.486
31.12.1703- Tokaido-Kashima 5.233-6.000
31.01.1605- Nankaido 5.000
02.03.1933- Sanriku 3.000-6.000
20.12.1946- To-Nankai 1.330
07.12.1944- To-Nankai 1.223

Fig.4. The Coastal Engineering Committee of the Japan Society of Civil Engineers released a map (23. March 2011) showing the heigths of the Tsunami on March 11.2011 in Japan. The highest value shown is 30meters with an average height of over 15 meter.

Bibliography:
ATWATER, B.F.; SATOKO, M.-R.; KENJI, S.; YOSHINOBU, T.; KAZUE, U. YAMAGUCHI, D.K. (2005): The Orphan Tsunami of 1700 Japanese Clues to a Parent Earthquake in North America. U.S.G.S. - University of Washington Press: 144
BRYANT, E. (2008): Tsunami - The Underrated Hazard. 2.nd edition Springer: 338
GATES, A.E. & RITCHIE, D. (2007): Encyclopedia of earthquakes and Volcanoes. Facts on file science library. 3th ed. New York: 346
GUNN, A.M. (2008): Encyclopedia of Disasters - Environmental Catastrophes and Human Tragedies. Vol.1. Greenwood Press, London: 733
KOZAK, J. & CERMAK, V. (2010): The Illustrated History of Natural Disasters. Springer-Verlag: 203
MINOURA, K.; IMAMURA, F.; SUGAWARA, D.; KONO, Y. & IWASHITA, T. (2001): The 869 Jogan tsunami deposit and recurrence interval of large-scale tsunami on the Pacific coast of northeast Japan. Journal of Natural Disaster Science, Vol. 23 (2): 83-88

The first modern principles of anti-seismic building

"When the earth shakes,

flee in the bamboo-forest."
Japanese proverb

Japan possesses the most severe guidelines for anti-seismic buildings in the world; surely this is one of the reasons that many constructions not affected by the Tsunami resisted to the earthquake. Also a map after the Mercalli earthquake scale (displaying the possible destructive effects of an earthquake) shows that on the mainland the reached intensity was "fortunately" lower than feared, because the epicentre laid far off the shores.
Fig.1. Mercalli intensity scale of the 8.9-9.1 magnitude earthquake of 11.03.2011 in Japan, after U.S.G.S. 2011.

Unfortunately preventing procedures or constructions for a Tsunami are virtually impossible, it were mainly these waves that caused much destruction and possibly killed thousand of people on the western coast of the island of Honshu (The German Aerospace Center (DLR) released satellite images and maps of the affected area on the shores of Japan). It seems also that it was the Tsunami that damaged severely the emergency system and cooling devices of the nuclear plant of Fukushima-Daiichi, a possible break of the containment of the nuclear material is now the greatest concern - Evelyn Mervine at Georneys posted an important interview about the anti-seismic guidelines, the damage and the actual situation at the power plant.

A sort of anti-seismic buildings were already known in ancient Japan, many Buddhist pagodas show some features that can minimize the dangerous oscillations of a building caused by an earthquake.
Some of these constructions tricks are possibly based on the observation of the biological characters of bamboo - the largest members of this grass family can reach a height of 30m.
In a pagoda the central column made of a single log is reaching deep in the ground like a root, it can swing in all directions and will so absorb most of the kinetic energy during an earthquake. The various floors of the pagoda can move independently and are connected to the inner central column by a complicated construction made of wood, acting like a spring or shock absorber it will also minimize dangerous movements.

The first modern principles of anti-seismic building were introduced at the beginning of the 20th century in Tokyo. The "Imperial Hotel" was commissioned in 1915 and inaugurated in 1923 as a luxury hotel for foreigners in imperial Japan.
It was projected by the American architect Frank Lloyd Wright (1867-1959), who visited Japan for a first time in 1905 and became enthusiast of Japanese Art.

Fig.2. The "Imperial Hotel" in Tokyo (1930s-40s), image from Wikipedia.

The site for the hotel seemed unfavourable for such a building, located in the seismic zone of Tokyo on a 2,4m thick organic soil resting on 20m of alluvial and unconsolidated sediments.
On such a ground engineers normally choose to build a deep basement, trying to reach competent rock mass or as deep as possible to anchor the building in the underground. Wright in contrast projected a very shallow basement, just reaching 2-3m deep. He argued that deep fundaments during an earthquake would transfer the oscillations from the ground to the building; however the alluvial mud of the construction site should absorb the seismic energy and the hotel float on the sediment like "a battleship floats on water."
The hotel had several ulterior features designed to minimize the destructive effects of an earthquake:

- The pool in front of the entrance was not only a decorative element, but provided a source of water for fire-fighting. This feature saved the hotel from the firestorm raging after the 1923 earthquake.
- Cantilevered floors extending to the outside of the building and balconies provided extra support for the floors.
- The walls were not constructed simply with bricks, but with a sort of innovative sandwich technology: reinforced concrete between an extern and intern layer of bricks.
- Tapered walls, thicker on lower floors, increasing their strength, with small openings and fewer windows than the upper floors.
- A light copper roof would not oscillate as strong as a massive roof and stress the construction, with the danger of collapse of the entire building.
- Seismic separation joints made of lead, located about every 20 m along the building; during an earthquake the single segments and floors should be able to shake independently without breaking.
- Separated hollows with suspended piping and wiring, instead of being encased in concrete, as well as smooth curves, making them more resistant to fracture. Wright recognized the danger of lacking water or electricity after an earthquake by the rupture of conduits or wires, also the danger of gas or fuel outpouring and alimenting fire.
- Dispensation of unnecessary decorative features on the outside of the hotel, which during an earthquake tend to break and can kill people.

The hotel was inaugurated the 1. September 1923, at 11.58 local time Tokyo was hit by a massive earthquake with a magnitude of 8.3 after Richter, 5.000 buildings collapsed in the entire city, thousands were heavily damaged.
Wright anxiously awaited information on his hotel, two weeks later he received a telegram from the Japanese entrepreneur Baron Kihachiro Okura reporting the following:

"Hotel stands undamaged as monument to your genius - Congratulations"

Wright's passing the telegram to journalists has helped perpetuate a legend that the hotel was unaffected by the earthquake, even the only building still standing in Tokyo. In reality, the building was damaged; the central section slumped, several floors bulged and four pieces of stonework fell to the ground.
The building's main flaw was its shallow foundation, during the earthquake the basement sunk by 0,6m into the liquefied mud and in the subsequent years continued slowly to sink into the underground. The damage and instability of the entire construction (also the passing time) finally resulted in the necessity to demolish the entire hotel in 1968.

However many of the other anti-seismic features introduced by Wright are still in use, and hopefully many new technologies will minimize the deadly effects of future earthquakes.

Bibliography:

WALKER, B. (1982): Earthquake. Planet Earth. Time Life Books: 154

Historic earthquakes in Japan

Japan is situated in the collision area of four great lithospheric plates: the Eurasian/Chinese Plate, the North American Plate, the Philippine Plate and the Pacific Plate. The continuous movements of these plates generate a lot of energy released from time to time in earthquakes of varying magnitude and effects and so unfortunately catastrophic earthquakes are nothing new for this region.

Destructive earthquakes occured in Japan for several times in the last centuries. From 1930 until today 10 stronger earthquakes have killed more than 18.000 people and destroyed hundreds of thousands of buildings. Many earthquake were associated also with devastating tsunamis.

Written Japanese records of strong earthquakes and their aftermath date back at least 1.600 years. Until 1860 however Japanese naturalists were less interested in exploring the cause of earthquakes than their effects, and mythical explanations and divine intervention prevailed.

Fig.1. This wood print of the year 1855 shows the god Kashima overlooking the sentence of the giant catfish Namazu, accused to have caused the devastating Edo-earthquake in 1855. A helper of the god - a daimyojin - uses a big hammer to beat the magic capstone into the head of the catfish and immobilize him. The scene is observed by an assembly of small catfishes, representing earthquakes of the past (from BOLT 1995).

In the year 1600 the Japanese nobleman Tokugawa Ieyasu chose the village of Edo (modern Tokyo) as his new residence, three years later it was the capital of the unified Japan. The city rapidly grew and soon reached hundreds of thousands of inhabitants - one of the largest cities at the time. Unfortunately this strategic position at the bay of Tokyo was and is also a highly seismic area.

Fig.2. Copper engraving published in 1669 by an anonymous European artist possibly illustrating an earthquake in Edo (modern Tokyo) in the year 1650. It is not clear if the artist experienced the earthquake himself or based this figure on eyewitnesses' accounts of unspecified earthquakes, nevertheless it presents one of the oldest known illustrations of a Japanese earthquake (after KOZAK & CERMAK 2010).

December 31, 1703 Japan was hit by a strong earthquake (with an estimated intensity of 8 after the Mercalli-scale), in Edo most of the buildings constructed of wood collapsed. More than 6.500 people were killed by a flood wave, which caused havoc in the bay of Sagami and on the peninsula of Boso. This earthquake and its aftermath effects, like flood and fire, killed estimated 150.000 people.

One of the most remembered earthquakes hit Tokyo on November 11, 1855 (the Ansei-Edo earthquake). It was one of the most destructive quakes (with a magnitude of 7.3), killing estimated 16.000 - 20.000 people. From this event many woodblock art prints still exist, displaying the destruction and telling of the despair of the survivors.
Fig.3. and 4. Anonymous contemporary woodcuts of Edo before and after the great 11 November 1855 magnitude 7.3 Ansei-Edo earthquake, from KITAHARA et al. 2003.
 
October 28, 1891, the agricultural Nobi region, north of the city of Nagoya, experienced an earthquake of magnitude 8. Modern buildings made of bricks as wooden traditional houses were heavily damaged or collapsed, hundreds of thousands became homeless and 7.000 people were killed.
The English geologists John Milne (1849-1913), who in 1880 founded the Seismologists Society of Japan, studied the effects of the earthquake and published an important monographic work "The great earthquake in Japan, 1891". The Japanese geologist Bunjiro Koto observed a superficial dislocation of the landscape by 4 meter as the origin of the earthquake and recognized a fundamental principle in seismology: that faults are not the result of an earthquake, but its cause.

During the second half of the 19th and early 20th century scientific research on earthquakes became rapidly established in Japan.
 
Fusakichi Omori (1868-1923), director of the Seismological Institute of Japan, studied the occurrence of earthquakes around Tokyo and wrote in 1922:

"Currently the immediate area of Tokyo is seismically quiet while in the mountains around Tokyo in a distance of about 60 kilometres there are often triggered earthquakes, which - although they are may felt in the capital - are in fact harmless, because the affected areas are not part of a larger destructive seismic zone.
Over time, the seismic activity in these areas will gradually diminish, meanwhile it will increase as compensation in the bay of Tokyo and will possibly cause a strong earthquake. An earthquake with an epicentre at some distance from Tokyo would be have a half-destructive, local impact."

One year later, September 1, 1923, the city of Yokohama and Tokyo were hit again by an earthquake, today remembered as the Great Kanto- earthquake with a magnitude of 7.9 on the Richter-scale and the epicentre situated in the bay of Sagami.
More than 99.000 people were killed by the collapse of buildings, a 10 to 12 meter high tsunami and a fire that raged for 2 days in the city. The bodies of possibly more than 40.000 people were never found. The first day of September is today a national day of remembrance for the dangers of earthquakes.

June 28, 1948 the American photographer Carl Mydans visited the city of Fukui to document the post-war development of this important industrial city. At 17.14 Mydans was surprised by a strong earthquake in the American military base, he remembers:

"The cement of the floor crashed. Dishes and tables were spun into our faces and we all found us in a mad dance…[]… when I found myself near the entrance, I moved into it's direction. But the floor slipped away under my feet and I rushed against a crumbling wall."

Mydans turned back to get his camera and in the next 15 hours documented the desperation and destruction of the 7.3 magnitude that destroyed Fukui and killed 5.131 people.

Fig.5. A woman tries to escape, avoiding large fissures opening in the ground. The photographs by Carl Mydans are unique documents of the terrible aftermath of the Fukui-earthquake of 28. June 1948.

According to Mydans, most of the victims perished entrapped under the debris or in the fire after the earthquake. Shocked by the lack of tools to remove the debris, Mydans promoted the distribution of emergency-boxes, equipped with an axe and other heavy tools.

In January 1995 the industrial city of Kobe was heavily damaged by an earthquake with a magnitude of 7.2 after Richter, the strongest earthquake in Japan since 1923. More than 6.000 people were killed and more than 300.000 people lost their homes.

The recent tragic earthquake of March 2011 with a magnitude of 8.9 (possibly 9.1, there is also a map showing the intensity after Mercalli) is covered by various geobloggers.

Fig.6. Map of Japan showing a selection of earthquakes with a magnitude greater than 7 after Richter in the last 100 years and major historic events (data from U.S.G.S. 2005, file download from Exploring Africa's Physical and Cultural Geography using GIS), see also Seismicity of the Earth 1900—2007, Japan and Vicinity.

Bibliography:

BOLT, B.A. (1995): Erdbeben - Schlüssel zur Geodynamik. Spektrum Akademischer Verlag, Berlin: 219
GUNN, A.M. (2008): Encyclopedia of Disasters - Environmental Catastrophes and Human Tragedies. Vol.1. Greenwood Press, London: 733
KITAHARAK, I. et al. (2003): Documenting Disaster, Natural Disasters in Japanese History, 1703-2003. Nat. Museum of Japanese History, Chiba.
KOZAK, J. & CERMAK, V. (2010): The Illustrated History of Natural Disasters. Springer-Verlag: 203

Tasman Glacier

The magnitude 6.3 earthquake that hit the last February 22 New Zealand not only caused havoc in city of Christchurch but also affected the Tasman Glacier, nearly 200 kilometres to the west of Christchurch.
Ice with the overall mass of 30 million tons broke off from the glacier tongue, a fragment nearly 1.200 meters long and 75 meters broad. Eyewitnesses report that the break-off caused a three meter high wave.
The glacier tongue was already instable and closed for tourists due to heavy rain in the last months. The water from above, in combination with the water of the lake, melted large quantities of ice and destabilized the glacier.
Like many glaciers worldwide also the Tasman Glacier is retreating since 1976, in the free space between the actual glacier and the moraines a ice-contact lake developed. The contact between ice and water accelerates melting and iceberg calving from the glacier.

Fig.1. Tasman Glacier with the Tasman Lake, the icebergs at the southern border of the lake are the remains of the collapse caused by the earthquake February 22 (ASTER-image by NASA, 02 March 2011). The comparison with older images show that mostly a part on the western lakeshore disappeared.