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Seismological Crust Models for KamLAND Experiment
Nozomu Takeuchi (University of Tokyo)
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What is CRUST5.1/CRUST2.0/CRUST1.0 ?Japanese community modelMethods for further improvements
Outline
Our Future Model
?
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Layered Structure of the Crust
Sedimentary Layers
Crystalline Crust
typical thickness < 1km
primarily constrained by geological data
typical thickness ~ 40 km
primarily constrained by seismological data
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What is CRUST5.1/2.0/1.0?models for crustal corrections (in obtaining mantle models)
global models obtained by using many extrapolations
Sedimentary Layer Structures
compilation of published models
obtained by compiling extrapolated models
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Assumption for Crystalline Crust Models for CRUST1.0
Conventional Seismological Dataset
Coverage of conventional seismologicaldata is not global.
Crystalline crustal structures are assumedto be identical in the same category ofgeological setting.
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41 ± 7 km 39 ± 7 km
43 ± 11 km 31 ± 6 km
31 ± 8 km 27 ± 8 km
Plausibility of the AssumptionVariance of the Crustal Thickness within the Same Geological Setting Categories
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Variance of the Mean Crustal P-Velocity
Plausibility of the Assumption
6.5±0.2 km/s 6.3±0.3 km/s
6.4±0.2 km/s 6.2±0.2 km/s
6.1±0.2 km/s 6.1±0.4 km/s
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What is the Japanese Community Model?models for simulating earthquake damage
strong focus on sedimentary structurescompilation of published models, a few extrapolations
sedimentary layers
crystalline crust
13 layersc.f.) 3 layers in CRUST1.0
3 layersc.f.) 3 layers in CRUST1.0
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Surface Geology Data Borehole Logging Data
Geological Layer Model for the Sedimentsetc.
Sedimentary Layer Model in Japan
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77,730 events
3,249,949 P-wave data2,273,571 S-wave data
768 stations
Crystalline Crust Model in Japan
Conventional Seismological Dataset
Conventional seismological datacovers all over Japan.
red: event, blue: station
No geological insight is requiredto obtain crystalline crust models.
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Comparison of Crustal Models
Total Crustal Thickness
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Comparison of Crustal Models
Upper + Middle Crust Thickness
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Comparison of Crustal Models
Upper Crust Thickness
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Comparison of Crustal Models
Thickness of the Sedimentary Layer
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Problems with the Community Model
hard to estimate uncertainties of the model
suffering from phase association problems
We cannot tell which of these 5 P waves is the initial phase.
hard to develop models with complex boundary shape / large number of interfaces
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0.01-0.05 Hz
0.05-0.1 Hz
0.1-0.5 Hz
0.5-1 Hz
1-5 Hz
5-10 Hz
all frequencies
Seismological Data Sensitive to Crustal Structures
conventionaldata
new data 1
new data 2
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Conventional Data New Data 1 New Data 2
(near field P & S) (surface waves) (converted phases)
Layer InterfaceLocations
Velocities inEach Layer
◎
◎
○
○
×
×
Resolving Power of Each Dataset
Overall ModelInitial Model Final Models
New Data 1 & 2 Conventional Data
Scheme for Obtaining Better Models
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Previous Efforts Using New Datasets
Stations Coverage
New Data 1 (short period surface waves) were usedto obtain crustal models.
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Problems with the Previous Efforts
Combining “New Data 2” will improve these problems.
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Using Crust 1.0 is a good starting point.
Using Japanese community model is the easiestway to write some papers but is not very exciting.
Improving existing crustal models should beinteresting both for seismologists and physicists.
Some Remarks for Future Studies
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