The 12th International symposium on deep seismic profiling of the continents and their margins continued the series of biennial meeting which involve specialists in the acquisition, processing and interpretation of lithospheric scale seismic profiling throughout the world. The symposium was held in 24-29th September 2006 at Shonan Village Center, Hayama, Japan. The Earthquake Research Institute (ERI), the University of Tokyo, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and National Institute for Earth Science and Disaster Prevention (NIED) organized the symposium. 125 geoscientists from 24 countries attended the symposium. They contributed 59 oral presentations including 6 key note talks and 121 posters for 14 scientific themes. In this 12th symposium, two special scientific themes focusing on structures of seismogenic zones and island arcs were allocated, since this is the first symposium held in Japan which is an island arc situated close to subduction seismogenic zones. In those special sessions, precise seismological structures of the island arcs were presented, and discussed their uniqueness and similarities by comparing with structures of the continents. Those discussions are one of the most fruitful outcomes from this symposium.

Fig 1. Group photo of the participants at in front of the Shonan Village Center.

The scientific themes and key issues discussed during the sessions are:
1. Japan Session
Outlines of geophysical features and geological evolution of Japanese islands.
2. Active Continental Margins
Including results from subduction zones, accretionary complexes, forearc basins, volcanic island arcs, back arc basins / ridges and vertical transform orogens. Including, but not limited to, reflection, refraction and OBS studies in these terrains.
3. Intra-continental Collision and Accretion
Continent-continent collisional belts. Involving crustal thickening, heating and internal deformation, the dynamics at the crust-mantle interface, and faults and fault zones which may define major discontinuities.
4. Continental Rifts and Basins
The geometry of rift basins, their extensional fault systems, bounding faults and internal structures. Also including features of the underlying layered lower crust.
5. Passive Continental Margins
Focusing on the geometry of passive margins (symmetrical or asymmetrical) their internal faults, the role of the middle / lower crust, the amount and distribution of extension on a crustal and lithospheric scale, deformation (pure shear versus simple shear). Including, but not limited to, reflection, refraction and OBS studies in these terrains.
6. Integrated Multidisciplinary Case Studies
Case studies that show the use of the wide angle range of seismic imaging studies that have been coupled with other disciplinary techniques. These techniques include, but are not limited to, magneto-telluric studies, potential field surveys, geochronological studies, thermo-mechanical modeling and rock properties analysis. The seismic imaging can include a range of techniques including
ehigh-resolution
f surveys, passive and active source surveys, two- and three-dimensional tomography studies.
7. The Continental Mantle
Studies of the deep lithosphere using the range of seismic techniques available. Also including studies involving mantle xenoliths and the core, and addressing issues such as nature of Moho, intra-mantle reflections and mantle characteristics.
8. Numerical Modeling of Heterogeneity and Anisotropy
Forward and inverse modeling of seismic attributes; synthetic seismogram modeling, and other numerical techniques.
9. Innovative Seismic Acquisition and Processing Techniques.
Those topics related to data collection and processing. Covering deep seismic survey design, 3D deep seismic data collection and processing, full wave-field recording and processing, wide-angle surveys and three component data. Including topics such as the meaning of deep reflectivity, differences between vertical-incident and wide-angle data sets, velocity differences, imaging steep faults, improving single/noise and active and passive sources.
10. Seismic Investigations Related to Mineral Resources and Volcano-plutonic System
The role of deep seismic surveys in understanding the role of the deeper crust in mineral and energy distribution. Including issues involving global metallogeny, geodynamics and ore deposit evolution, beyond oil exploration ? the basement, mineral deposits and seismic studies. Also addressing the fundamental issues of imaging and modeling of field systems.
11. Subduction Structures of Megathrust Zone
Seismic images at the subduction megathrust zones from reflection and wide-angle reflection/refraction surveys, and tomography studies. Addressing the detailed mapping of the source areas of megathrust earthquake.
12. Seismic Investigations for Disastrous Earthquake Areas
Results from seismic investigation in disastrous earthquake areas. Imaging and mapping of source and active faults and regional characterization in disastrous earthquake areas by seismic surveys using active and passive sources.
13. Classic Transect
The process of documentation and description of
eClassic
f seismic transects throughout the world. Covering issues including
ewhat are their characteristics
f and
ewhat we have learnt from them
f.
14. Japan Transect (poster session only)
Results of seismic imaging and geological surveys in Japan to traverse Japanese islands from trench to back arc. The seismic imaging with high-resolution surveys, passive and active source surveys, two- and three-dimensional tomography studies.
In order to make the widest dissemination of the results presented in the symposium, the organizing committee has made preliminary arrangements with Elsevier journal Tectonophysics for a Special Symposium Proceedings issue.
An additional important task of this symposium is to stimulate debate on key points that can have significant influence in future research related seismic studies on the continents and their margins. In order to meet those demands, four special interests business meetings were held in the evenings. They were:1. Seismic investigation in Asia; upcoming effort and opportunities for collaborations, 2. TopoEuro and EuroArray, 3. Organizing the next Commission o0 Controlled-Source Seismology (CCSS), 4. CGCP Project 474
gImage and the Earth
fs Crust and Upper mantle
h
In the end of the symposium, it was officially announced that the next symposium will be held in Finland in 2008 and will be organized by University of Helsinki and Geological Survey of Finland.

Fig. 2 Logo of the 12th International symposium on deep seismic profiling of the continents and their margins

Fig. 3 Shonal village center