Seismological Crust Models for KamLAND Experiment

Nozomu Takeuchi (University of Tokyo)

What is CRUST5.1/CRUST2.0/CRUST1.0 ?Japanese community modelMethods for further improvements

Outline

Our Future Model

?

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

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

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.

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

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

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

Surface Geology Data Borehole Logging Data

Geological Layer Model for the Sedimentsetc.

Sedimentary Layer Model in Japan

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.

Comparison of Crustal Models

Total Crustal Thickness

Comparison of Crustal Models

Upper + Middle Crust Thickness

Comparison of Crustal Models

Upper Crust Thickness

Comparison of Crustal Models

Thickness of the Sedimentary Layer

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

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

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

Previous Efforts Using New Datasets

Stations Coverage

New Data 1 (short period surface waves) were usedto obtain crustal models.

Problems with the Previous Efforts

Combining “New Data 2” will improve these problems.

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