geophysical observations of the 100 km region around kamland tohru watanabe dept. of earth sciences...

Geophysical observations of the 100 km region around KamLAND

Tohru Watanabe

Dept. of Earth SciencesUniversity of Toyama (Japan)

Today’s Talk

1. Geophysical observations around KamLAND

2. Laboratory data on seismic velocities in rocks around KamLAND

Toyama

KamLAND

Niigata-Kobe Tectonic Zone (High strain-rate zone)

Atotsugawa Fault 1858 Hiestu Earthquake (M7)

Geophysical Observations Seismological Obs. MT surveys Gravity Obs.

1. Geophysical Observations

Iio et al. (2002) EPSL

Depth Contours of Pacific and Philippine Sea Plates

Nakajima et al. (2010)

KamLAND

NKTZ

Seismological Studies on Crustal Structure

Nakajima et al. (2010)

NKTZ

Iidaka et al. (2003)

Kato et al. (2006, 2007)

Nakajima et al. (2010)

Iidaka et al. (2003)

Seismic refraction survey

6 explosive sources

391 seismic stations

L~250 km

P-wave velocity structure (Iidaka et al., 2003)

N S

Toyama Plain (sediments)

KamLAND

Kato et al. (2006, 2007)

2006

2007

Travel-time Tomography

Explosive sources +Local Earthquakes

Nakajima et al. (2010)

P-wave velocity structure (Kato et al.,2007)

Toyama Plain (sediments)

Nakajima et al. (2010)

Nakajima et al. (2010)

Travel-time Tomography

P-wave velocity perturbationsD=0 km D=5 km D=10 km

D=15 km D=25 km D=40 km

Nakajima et al. (2010)

Structure along Atotsugawa Fault

Hakusan Tateyama

Nakajima et al. (2010)

Velocity Perturbations across Atotsugawa Fault

SN

Nakajima et al. (2010)

Summary of Seismological Observations

Seismological observations have revealed

(1) A complicated configuration of subducted plates

(2) Low velocity regions associated with active volcanoes

(3) Surface low velocity regions caused by thick sediments

2. Laboratory Data on Seismic Velocity

Upper, Middle Crust (D<10 km) Kagami and Watanabe (2009)

Surface rocks

Lower Crust (D>20 km) Nishimoto et al. (2008) Xenoliths (Rocks collected by magma

during its ascent)

Surface geology around KamLAND

after Yamada et al. (1989)

11 rock samples

P-wave Velocity vs Confining Pressure

D~7kmD~2km

Granodiorite (TKA-b1)

Density vs Vp (180MPa)Hida granites

Hida metamorphic rocks

Vs vs Vp (180 MPa)Hida granites

Hida metamorphic rocks

Comparison with Observed Velocity

Hida metamorphic rocks (+Hida granites)

Kato et al. (2007)

KamLAND

Ichino-megata

KamLAND

Ichino-megata mafic-ultramafic xenoliths

Lower Crust Xenoliths

Iio et al. (2002) EPSL

Nishimoto et al. (2008) (1) Hornblende gabbro (2) Hornblende-pyroxene gabbro (3) Amphibolite (4) Pyroxene amphibolite (5) Hornblendite

Measured Velocity at High T and High P

Nishimoto et al. (2008)

D~25 km

Inference of Lower Crustal Material

Nakajima et al. (2010)

D=25 km

Rock + aqueous fluids

D=25 km

Pyroxeneamphibolite

Hornblende-pyroxenegabbro

Nakajima et al. (2010)

Summary of Laboratory Data

Upper and middle crust Hida metamorphic rocks Hida granites

Lower crust Pyroxene amphibolite Hornblende-pyroxene gabbro