RAPID SOURCE PARAMETER DETERMINATION AND EARTHQUAKE SOURCE PROCESS IN INDONESIA REGION Iman Suardi Seismology Course Indonesia Final Presentation of Master Report August 28, 2007 International Institute of Seismology and Earthquake Engineering, Building Research Institute, Tsukuba, Japan, 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 CMT Retrieve 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; E). before after

Earthquake event list from the Global CMT (4 March 2007 – 25 April 2007). Data Retrieval from IRIS-DMC No.EventyyyymmddLocation M W Global CMT Depth (km) event1 event2 event3 event4 event5 event6 event7 event S, E -8.08S, E -0.73S, E 4.19N, E 1.30N, E 0.98N, E 1.55N, E 2.72N, 95.47E IRIS-DMC stations

Magnitudes Scales Body Wave Magnitude, mb m b = Log 10 (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, M s, Gutenberg (1945) M s = Log 10 (A/T) Log 10 ∆ + 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, M w, Kanamori (1977) M w = (Log 10 M o – 9.1)/1.5, M o (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). M wp = M w Body Wave Magnitude, mb m b = Log 10 (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, M s, Gutenberg (1945) M s = Log 10 (A/T) Log 10 ∆ + 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, M w, Kanamori (1977) M w = (Log 10 M o – 9.1)/1.5, M o (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). M wp = M w THEORY AND METHODOLOGY

Magnitude JMA, M JMA using accelerometer 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: A D is the maximum amplitude (µm), A Z isvertical component of velocity,, Attenuation Function depends on epicentral distance ∆ and on the focal depth, H, C V depends on instrumental conditions of seismographs. Continued …

Empirical Formula of Richter’s Magnitude Empirical Formula A New Magnitude for BMG Find coefficients Least Square Method

Least Square Method find coefficient a 1, a 2, and a 3 minimum event station unknown constant unknown

Unit impulsive slip Propagate wave Observed station Green’s function Green’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

Empirical Equation Type2: Type1: RESULTS AND DISCUSSIONS The Magnitude Determination of BMG

Type2: Tsuboi’s formula A Calculated Magnitude of BMG 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. 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.