NATIONAL CHENG-KUNG UNIVERSITY – CRUSTAL DEFORMATION 1 RELATIONSHIP BETWEEN FAULT AND EARTHQUAKE IN SUMATERA, INDONESIA 1. INTRODUCTION Indonesia is located at the triple junction of the Australian Plate, Eurasian Plate, and Pacific Plate. The Australian Plate is converging with the southeastern segment of the Eurasian Plate, called the Sunda Plate, at a relative plate motion rate of approximately 60 mm/a. This plate motion is oblique to the Sumatran Subduction Zone. The boundary-parallel shear motion of the convergence transpires mainly along the Sumatran Fault, while the boundary-perpendicular convergent motion is accommodated by underthrusting along the Sunda Megathrust at a rate of approximately 45 mm/a. Because of these complex tectonics, Indonesia is an earthquake-prone country. Figure 1 shows that the tectonic and geographic location of Sumatran Fault. The great Sumatra – Andaman earthquake and Tsunami of 2004 was dramatic reminder of the importance of understanding the seismic and tsunami hazards of subduction zones. There’s several earthquakes happen in Sumatran which are in March 2005 Sunda Megathrust ruptured producing moment magnitude amount 8.6; in 1797 producing moment magnitude amount of 8.8 and in 1833 producing moment magnitude amount of 9.0 at the same area. There is several ways to understand between the relationship between fault and earthquake. The commonly method is using GPS measurements, join inversion of teleseismic body wave data and strong ground motion data, InSAR, etc. Here, we shows the relationship between those topics using two paper and what’s the historical earthquake occured to understand the patterns. Those earthquakes in Sumatran are correspond to each other and connected by the geographical of Sumatran Island. Figure 1. Tectonic and Geographic Location of the Sumatran Fault (GSF). The red triangles mark the volcanoes. 2. METHODS AND DATA From different cases (Mentawai Earthquake and Sumatran – Andaman), this paper using joint inversion of teleseismic and strong ground motion data to estimate 2010 of the Mentawai tsunami earthquake rupture process. The data from IRIS – DMC and BMKG station near the mainshock occurred. InSAR and GPS measurement to understand partial rupture of a locked patch of the Sumatra megathrust during the 2007 earthquake sequence. The data from calculation of GPS measurement in the field and also interpretation of InSAR image. All of these datas are use for understanding the relationship between fault and earthquake. For all details it will explain at results and discussion section. 3. RESULTS AND DISCUSSION From combining two papers we know that the relationship between earthquake and fault is Earthquake occur on Faults. Strike – slip earthquakes occur on strikes – slip faults, normal earthquakes occur on normal faults and thrust earthquake occur on thrust or reverse faults. When an earthquake occurs on one of these faults, the rock on one side of the fault slips with respect to other. The fault surface can be vertical, horizontal, or at some angle to surface of the earth. The slip direction can also be at any angle. From this relationship, we take two papers as an example. It can reinforce our statement about the relationship between earthquake and faults. In Paper 1 (Estimation of the 2010 Mentawai tsunami earthquake rupture process from joint inversion of teleseismic and strong ground motion data) shows The 2010 Mentawai earthquake generated a locally devastating tsunami much larger than expected based on the seismic magnitude. Source process inversion results indicate a shallow dip, consistent with an origin on the Sunda Megathrust. The rupture nucleated around the hypocenter and propagated to the southwest and broke the first asperity centering at 14 km from the epicenter with maximum slip amounting to 3.9 m, then propagated along the strike direction to the northwest where the second asperity was broken, which was centered about 78 km from the epicenter. this paper identify this earthquake as a tsunami earthquake because of its excessively long rupture duration and its generation of a greater than expected tsunami. However, there are large differences in slip distributions from the different modeling methods and datasets. Although this paper cannot reconcile these complexities and large uncertainties on the amount of slip still exist, this paper found the conclusion that the majority of slip occurred far from the islands at very shallow depths to be robust. As mentioned above, many large earthquakes have occurred in this region. After comprehensive analysis, the 2010 Mentawai Mw7.8 earthquake ruptured immediately updip of and was probably triggered by stress changes following the September 2007 Mw8.5 Sumatran earthquake. This area may have last ruptured as part of the 1797 Mw8.6 and 1833 Mw8.9 events, described by Natawidjaja et al. as having about 18 m of megathrust slip to explain the co-seismic uplift. Further north, the 2005 Mw8.6 Nias earthquake ruptured the same approximate area. Available high resolution