The survey of Lake Kawaguchi is already done !

We finished the coring in Lake Kawaguchi, it was a real success!  Lake Kawaguchi is a shallow lake with a maximum depth of 12 m. It is characterized by three sub-basins – Western, central and East basins. We investigated two sites, one in the western basin and one in the central basin.

The Fuji Five Lake survey has started !

On Monday, the platform arrived from Hamana-ko to Kawaguchi-ko. At the end of the day, we were ready to core. The aim of the survey is to get long cores from the Fuji Five Lakes in order to retrieve the seismic history of the Nankai Through. During this month, we will investigate Lake Kawaguchi, Lake Motosu and Lake Sai. We will spend one week in Lake Kawaguchi and Lake Sai. Our best target is the Lake Motosu where we will be for two weeks. This year, we decide to not investigate Lake Yamanaka for several reasons. Lake Yamanaka is very close to Fuji volcano and highly exposed to eruptions. The study of the 1998 old borehole revealed a lot of scoria layers and we were not sure that our equipment could go through them. Because our coring system was struck in Hoei scoria (1707A.D.), the age of short cores taken last year is relatively well constrained. In 300 years, Lake Yamanaka has not recorded any turbidites. This is why, this year, we will focus on the other three lakes. In our long cores, we expect to find turbidites triggered by earthquake that allow us to compare the earthquake fingerprint of each lake… But first, we need to hammer!

The platform on Lake Kawaguchi

Every end is a new beginning

Our working days on coastal Lake Hamana are now definitively over. The platform has been relocated to the Fuji area, where coring operations on Lake Kawaguchi were started.  

Unfortunately, we did not succeed in retrieving all missing core sections on site 3 and site 4 of Lake Hamana, since very strong winds threw a spanner in the works and we were not able to sail out during the last two days. Nevertheless, we now possess sediment samples up to a depth of 9 m below the lake floor, from four different locations along a N-S transect throughout the central basin. Such transect allows us to map the extent and lateral variations of tsunami deposits, which will be traced by executing a series of sedimentological, geophysical and geochemical analyses.

But first… our cores have to be shipped back to Belgium. This will be done at the end of November, after the Fuji survey is finished as well.

Sneak peaks of Mount Fuji from Lake Hamana

Entering the last week

Having the checkered flag of our Lake Hamana piston coring mission in sight, we can already look back at many days of hard work and dedication. However, we still need to complete a few things.

We have been sampling sediment from four consecutive sites along a N-S transect within the lake’s central basin, north of the tidal delta. Two of these sites are entirely finished (site 1 and 2), whereas we still have to take six more 2 m piston core sections from the northern two sites (site 3 and 4).   

Location map of Lake Hamana (left) and bathymetry of the lake basin with indication of our coring sites, yellow ones are finished, red ones still need to be completed (right)

If I had a hammer…

I’d hammer in the morning, I’d hammer in the evening…

Two weeks have passed since we started taking cores from our platform on Lake Hamana and loads of mud and sand has been lifted out of the lake floor. Our Belgian coring team is starting to work like a well-oiled machine. Hence, about time to introduce you to our floating home and how we manage to sample more than 8 m of bottom stratigraphy.

Our platform is held in position by four anchors and consists of four rubber floaters, a 3x4 m standing surface with a central opening and a tripod to which three winches are fastened. Each of these winches holds part of the coring equipment, which is guided through pulleys at the crest of the tripod. One winching cable is attached to the hammer weight, one to the piston and one to the entire system (coring barrel, hammer weight and piston).

Leaving the marina

A new field season for QRN

Last year (Oct-Nov), the QRN team came together in Japan for conducting exploratory surveys on the Fuji Lakes and the coastal Hamana lake area. This exploration comprised the acoustic imaging of lake bottoms as well as sediment sampling in lakes and on land. Right now, a second field season has come on stream, starting with an in-depth investigation of the Hamana Lake deposits (Oct) for which Ghent University shipped a coring platform (British Antarctic Survey) to Japan. 

In preparation for this year’s fieldwork on Lake Hamana, last year’s data and samples (short gravity cores) were analysed thoroughly in order to retrieve information on prevailing depositional processes, average sedimentation rates and the possible presence and lateral extent of tsunami deposits within the lake basin. Based on that knowledge, a set of sites were selected for collecting long cores (up to 8 m of depth). Hopefully, these long records will shed light on recurrence patterns of tsunamis along the Nankai Trough.

Pouring rain during platform build-up at the Suzuki Marina in Washizu.

QRN field recce photo diary

Marc, Atsunori, Osamu, Vanessa, Masanobu, Miyairi, Ed, Yusuke and a few others have spent the last few days meeting to discuss the next targets for the onshore field campaign. We spent time travelling along the Shizuoka coast to see some potential new sites and also met up with the QRN lake coring team, who are a week into their campaign on Lake Hamana (More to follow from Evelien Boes soon...). Here are a few photos from the lab and field.

We started the trip checking out some cores stored in Tsukuba, headquarters of the Geological Survey of Japan

INQUA 2015

As highlighted last month, the QuakeRecNankai project was out in force last week at the 19th quadrennial congress of the International Quaternary Union (INQUA) in Japan. The meeting, held at the Nagoya Congress Centre, spanned 7 days and was attended by 1,790 earth scientists from 68 countries and regions.

Members of the project gave 5 talks and 4 posters on the latest research on Nankai Trough earthquakes and tsunamis, with Osamu Fujiwara also chairing a successful session on assessing earthquake and tsunami risks using geological records.

A QuakeRecNankai meeting attended by no less than 15 project members allowed us to discuss upcoming fieldwork and welcome Atsunori Nakamura (Geological Survey of Japan, AIST) to the project.

The week ended with a notable success, with Evelien Boes receiving a thoroughly deserved best student poster award.

Laura Lamair introduces the Fuji Five Lakes

Ed Garrett summarises the current state of palaeoseismic research along the Nankai Trough

Evelien Boes talks through her award winning poster on Lake Hamana

Yoshiki Sato with his poster on biostratigraphic records from Lake Hamana

Ed Garrett with his poster on dating tsunami deposits

Laura Lamair discusses her poster on turbidites in the Fuji Five Lakes

Evelien Boes wins INQUA best student poster award

Evelien Boes won one of the Student Poster Awards at the XIX INQUA Congress (Nagoya, Japan), with her poster "Exploring the potential of Lake Hamana (Shizuoka Prefecture, Japan) to hold a long and reliable sedimentary record of paleo-earthquakes and -tsunami along the Nankai-Suruga Trough" - Boes, E., Fujiwara, O., Garrett, E., Lamair, L., De Batist, M., Heyvaert, V., Yokoyama, Y., Miyairi, Y., Irizuki, T., Riedesel, S., Brückner, H., Hubert-Ferrari, A. & the QuakeRecNankai Team".  

Congratulations to Evelien! 

Evelien discusses her poster with Shishikura-san from the Geological Survey of Japan

Presentations at INQUA

The International Quaternary Union, INQUA, holds a quadrennial meeting, with Nagoya, Japan, being the location chosen for this year. The QuakeRecNankai team will be well represented, with presentations and posters on all three strands of our project. Here's the full list of presentations by QRN team members on earthquakes along the Nankai Trough:

Tuesday 28th July                                                                   

Laura Lamair                   T06-P07                 14:00-15:30        The last 300 years of sedimentation in the Fuji Five Lakes: the impact of natural disasters with a special focus on earthquakes (poster)

          

Friday 30th July

Ed Garrett                        T21-07                    12:40-12:55        Progress in paleoearthquake and paleotsunami research along the Nankai Trough following the 2011 Tohoku earthquake

Yoshiki Sato                     T21-08                   17:00-17:15        Middle to Late Holocene environmental changes in the incised valleys around Lake Hamana suggesting the great earthquakes along Nankai Trough

Osamu Fujiwara              T21-09                    17:15-17:30        Holocene coastal deformation of the Hamamatsu plain related to the great earthquakes along the eastern Nankai Trough

Mansanobu Shishikura   T21-10                  17:30-17:45        History of past great earthquakes along the Nankai Trough, deduced from various geological records in the southern part of the Kii Peninsula, Japan                                      

Evelien Boes                T21-P09               14:00-15:30        Exploring the potential of Lake Hamana (Shizuoka Prefecture, Japan) to hold a long and reliable sedimentary record of paleo- earthquakes and -tsunami along the Nankai-Suruga Trough  (poster)

                                   

Saturday 1st August        

Laura Lamair                    G02-05                   12:10-12:25        Late Holocene History of the Fuji Five Lakes (Japan)

Ed Garrett                      C13-P01                14:00-15:30       Radiometric and luminescence dating of historical tsunamis and storm deposits from Shirasuka, south central Japan (poster)

European Geoscience Union annual meeting, Vienna

A number of QuakeRecNankai collaborators gathered in Vienna for the 2015 European Geoscience Union annual meeting. Geoscientists descend on the Austrian capital for the five day meeting every year; the 2015 meeting saw over 11,000 scientists from 108 countries give more than 14,000 presentations in 577 separate sessions.

The presentations included a poster on the QuakeRecNankai project, "Geological evidence for historical and older earthquakes and tsunamis along the Nankai Trough, Japan", which was a contribution to the session on "Large Earthquake and Tsunami Activity" held on Monday afternoon. The poster summarised published geological evidence for past earthquakes and tsunamis along the Nankai Trough and, for the first time at a major international conference, introduced the QuakeRecNankai project. The abstract for the poster can be found here.

Spotlit: the QRN poster

The 4th International Tsunami Field Symposium, Thailand

From 22^th to 27^th of March the QRN Team, represented by Vanessa Heyvaert, Helmut Brückner, Evelien Boes and Svenja Riedesel, attended the 4^th International Tsunami Field Symposium in Phuket, Thailand. Kruawun Jankaew and her team created an unforgettable conference including three days of fieldtrips within the breathtaking landscape of southern Thailand.

Abstract book and field guide booklets, led by Kruawun Jankaew

Attended by researchers from all over the world, the symposium was dedicated to the 10th anniversary of the 2004 Indian Ocean Tsunami (IOT). Beside three very informative keynotes held by Kerry Sieh (EOS, NTU, Singapore), Kenji Satake (ERI, University of Tokyo) and Kazuhisa Goto (IRIDeS, Tohoku University), the participants presented their diverse research projects, which were all related to earthquakes and tsunamis. As a result of different research focuses (Science, Technology and Disaster Mitigation), the conference offered a great opportunity to discuss these topics and meet old and new colleagues.

During the three days of fieldtrip to Phuket, Khao Lak and Phra Thong, it was possible to observe sedimentological evidences of the 2004 IOT, changes in landscape and human interactions as well as facilities of the tsunami warning and secure system. Tsunami memorials remind us of the catastrophic happenings of December 26, 2004.

Looks like painted – the IOT sediments on Phra Thong Island

Tsunami evacuation routes of Kamala Bay

Boat 813 – today approx. 2 km inland, was moved to its present position by the IOT 2004

Multi-Sensor Core Logging (MSCL)

To be able to study the stratigraphic sequences caught in our coring tubes, plastic liners first need to be opened. We use a specialised core splitter with two circular saws in order to make parallel, lengthwise incisions, which can be cut through easily with a knife. Once the liner has been divided into two halves, the inside sediment still has to be separated. Because surface deposits from the bottom of Lake Hamana appeared to be extremely runny and water saturated, we prefer to use metal plates for splitting. Two of these plates are being pushed through the lengthwise incisions and through the sediment until hitting the underlying table top, after which they can be pulled apart. One after the other, the metal plates are slid off the core halves, providing us with clean sediment surfaces.

Some additional, manual retouches might be necessary for acquiring good images with the linescan photography setup, which is part of the Ghent University GEOTEK Multi-Sensor Core Logger (MSCL) (http://www.geotek.co.uk/products/mscl-s-). The MSCL is a tool for non-destructive, downcore analyses of several geophysical properties of the sediment, such as density, magnetic susceptibility and colour spectrophotometry. Density values signify how tightly the matter is packed together and are a good indicator for porosity and lithology variations. Magnetic susceptibility (MS) is the degree in which a material magnetises in response to an applied magnetic field. Positive measurements suggest that the analysed sediment might be paramagnetic, ferromagnetic, ferromagnetic or antiferromagnetic. MS data can thus be extremely useful when looking for changes in sedimentary provenance and/or diagenetic processes. Colour records from the spectrophotometer provide true colour representations of split core surfaces before oxidation processes can take place. Therefore, it is of major importance that MSCL logging is done immediately after core opening. Moreover, sediment colour reflects compositional elements and mineralogy as well, complementing density and MS data.

Each of these properties are measured stepwise with contact point-sensors attached to the MSCL. Logging results in full downcore profiles of the above properties and can be used for further study. For instance, stratigraphic sequences will be described macroscopically, paying special attention to sediment colour, texture, structure, grain size, contacts etc. These macroscopic observations can then be correlated with the geophysical properties, hopefully enabling us to recognise some event deposits. 

The below (highly speed up) timelapse video shows how split sediment cores move through the linescan setup of the GEOTEK MSCL. Meanwhile, several geophysical properties are measured and acquired data are shown on the computer screen.    

Meeting in Tsukuba

Planning for the QuakeRecNankai 2015 field season is underway. Marc de Batist (Ghent University) and Vanessa Heyvaert (Geological Survey of Belgium) travelled to Tsukuba, home of the Active Fault and Earthquake Research Centre, to discuss plans for fieldwork on the Fuji Five Lakes and Lake Hamana with QRN collaborators Osamu Fujiwara (AIST), Yosuke Miyairi (University of Tokyo), Shinya Yamamoto (Mount Fuji Research Institute) and Stephen Obrochta (Akita University). The team will be back in the field this autumn to continue the search for evidence for past earthquakes and tsunamis along the Nankai Trough.