RAPID SOURCE PARAMETER DETERMINATION AND EARTHQUAKE

SOURCE PROCESS IN INDONESIA REGIONIman Suardi Seismology

Course Indonesia

Final Presentation of Master Report August 28, 2007

International Institute of Seismology and Earthquake Engineering, Building Research Institute, Tsukuba,

Japan, 2006-2007

Supervisor:DR. Akio KATSUMATA (MRI-JMA)

Prof. Yuji YAGI (Tsukuba University)

INTRODUCTION

DATA

THEORY AND METHODOLOGY

RESULTS AND DISCUSSIONS

CONCLUSION

RECOMMENDATION

CONTENTS

Indonesia Earthquake Information and Tsunami Warning Center (InaTWS end 2008)

INTRODUCTION

Tectonic Setting of Indonesia

Propose a new rapid method to determine earthquake magnitude

release a new BMG magnitude tsunami early warning,

Determine focal mechanism and seismic moment,

Determine moment magnitude,

Compare moment magnitude with the above magnitude.

Purpose of This Study

Distribution Of The New Accelerometer Network Of BMG

data range from 4 March 2007 – 25 April 2007

DATA

Raw Data from Accelerometer TSA100S from Nanometrics Inc.

(continuous waveform data).

Convert to XFiles format

Convert to Seed format

Convert to SAC (by using rdseed4.6)

using software Data Playback prepared by Nanometrics Inc.

Continuous waveform data from 4 March – 25 April 2007

Calculated Magnitude of BMG

Moment Tensor Inversion

Event data collection from Global CMTRetrieve waveform data from internet (IRIS network / FDSN-GSN

stations)Remove instrument responses

Data Preparation

The performance of waveform before converting and after converting into displacement record for event5 (2007/03/17, M6.2, depth 40.7 km, 1.30N; 126.37E).

before

after

Earthquake event list from the Global CMT (4 March 2007 – 25 April 2007).

Data Retrieval from IRIS-DMC

No. Eventyyyymmdd

LocationMW Global

CMT

Depth (km)

12345678

event1event2event3event4event5event6event7event8

2007030920070313200703152007031520070317200703262007033120070407

-6.34S, 130.23E-8.08S, 117.94E-0.73S, 127.60E4.19N, 127.04E1.30N, 126.37E0.98N, 126.05E1.55N, 122.63E2.72N, 95.47E

5.65.65.45.26.25.55.66.1

149.324.112.018.540.729.021.912.0

IRIS-DMC stations

Magnitudes Scales Body Wave Magnitude, mb

mb = Log10(A/T) + q(∆,h), where: A(µm), Amplitude (SP); T(s), Period;

∆ (deg), Epicentral Distance; h(km), Focal Depth.

Based on amplitudes of P waves (T~1 sec) not appropriate for large earthquake.

Surface Wave Magnitude, Ms, Gutenberg (1945)

Ms = Log10(A/T) + 1.66Log10∆ + 3.3, where: A(µm), Amplitude (LP); T(s), Period; ∆ (deg), Epicentral Distance.

Based on amplitudes of surface waves (T~20 sec) easy to determine, underestimate size for great earthquakes.

Moment Magnitude, Mw, Kanamori (1977)

Mw = (Log10Mo – 9.1)/1.5, Mo (Nm) = µDS : Seismic Moment

where: µ rigidity; D Displacement; S Fault Area.

Based on moment tensor solutions such as USGS MT solutions and Global CMT

solution No saturation, Difficult to determine.

Broadband Moment Magnitude, Tsuboi et al. (1995).

Mwp = Mw + 0.2

THEORY AND METHODOLOGY

Magnitude JMA, MJMA using accelerometer

DDDD CHAM ),(log

For distance within 2000 km

, Tsuboi’s formula (1954).

Shallow earthquake < 60 km.

, Katsumata’s formula (2004).

R > 30 km, ∆ < 700 km , Funasaki et al.

(2004) R > 5 km, ∆ < 700 km

where: AD is the maximum amplitude (µm), AZ isvertical component of velocity , , Attenuation Function depends on epicentral distance ∆ and on the focal depth, H, CV depends on instrumental conditions of seismographs.

),( HD

VVZV CHAM ),(log)85.0/1(

83.0log73.1log 1010 DAM

Continued …

DDWDD RMA 1010 loglog

Empirical Formula of Richter’s Magnitude

Empirical Formula

A New Magnitude for BMG

Find coefficients Least Square Method

Least Square Method find coefficient a1, a2, and a3

j i

jijij bRaA 22 )log(log

j i

wijij MaaRaA 2132 )log(log

minimum

minimum

event stationunknown

constant

constant

unknown

WMaa 13

unknown

Unit impulsive slip

Propagate wave

Observed station

Green’s functionGreen’s Function

The response function, effect of propagation, with unit impulsive slip

and / or force.

Determination of Source Parameter:

faulting type Focal mechanism,

earthquake size Seismic Moment, Moment

Magnitude.

Moment Tensor Inversion

jcccjqq

qj etTzyxtGmtd

)(),,,()(5

1

jjcccjj zyxtT emGd ),),(( ,

5

4

3

2

1

11

222

111

1

2

1

,

)( )(

)( )( )(

)( )( )(

,

)(

)()(

51

521

21

mmmmm

tGtG

tGtGtG

tGtGtG

td

tdtd

mns

mns

mud

mud

mud

mud

mud

mud

ns

ud

uds

mGd

Empirical Equation

321 loglog aRaRAMa

321 loglog aRaAMa

3617185.000160585.0loglog RRMA

88362.1log15048.2log RMA

Type2:

Type1:

RESULTS AND DISCUSSIONS

The Magnitude Determination of BMG

321 loglog aRaAMa Type2:

Tsuboi’s formula

83.0log73.1log MA

A Calculated Magnitude of BMG 88362.1log15048.2log RMA

88362.1log15048.2log 1010 RAM DBMG

or

Graph of Comparison of maximum amplitudes of three type of magnitude calculation plotted against

epicentral distances for each events.

Graph of comparison between the moment magnitude from Global CMT and

the calculated magnitude of BMG (type2).

Difference between the calculated magnitude of

BMG and the moment magnitude of Global CMT

plotted against the moment magnitude of Global CMT.

Difference between the calculated magnitude of BMG

and the moment magnitude from Global CMT plotted

against the depth of earthquakes.

Graph of difference between observed maximum amplitudes and estimated ones plotted against

hypocentral distances for all the events.

(a)

(b)

The results of moment tensor inversion of 5 earthquake events. (a) Assumed

source time function and focal mechanism. (b) Theoretical waveforms

(red curves) from a point source and observed waveforms (black curves).

Moment Tensor Inversion

Graph of comparison between the moment magnitude from Global CMT and the moment

magnitude obtained from moment tensor inversion.

Graph of comparison between the magnitude determination of BMG and the moment magnitude obtained from moment tensor inversion.

Comparison of focal mechanism from Global CMT (blue color) and from moment tensor

inversion (red color). Green stars denote epicenters; red triangles denote

accelerometer station used for calculating the magnitude of BMG.

The magnitude determination of BMG:

The consistency with the other magnitude determination, the magnitude determination of BMG is still sufficient and reliable for shallow earthquakes less than 150 kilometers and the hypocentral distance less than 1,000 kilometers,

The seismic moments and moment magnitude estimated by moment tensor inversion are generally consistent with those of Global CMT,

The magnitude determination of BMG is systematically consistent with the results from moment tensor inversion;

For the rapid earthquakes indicated by short source duration time, the magnitude determination of BMG will become overestimated, The slow earthquakes indicated by long source duration time, the magnitude determination of BMG will become underestimated.

88362.1log15048.2log 1010 RAM DBMG

CONCLUSION

RECOMMENDATION

The formula of the magnitude determination of BMG could be improved after seismic records are accumulated in BMG. Collecting and storing data should be well managed. The long time collected data is of an urgent necessity in order to make reliable coefficients of this formula.

The dense distribution of accelerometer station should be realized in order to obtain high quality of data.

Intensive study of magnitude determination of tsunami earthquakes will give advantage to improve the reliability of this formula.