SOURCE PARAMETER INVERSION: DAMPED ISOCHRONE INVERSION

• Main Author: I GEDE PUTU FADJAR SOERYA DJAJA (NIM: 22415002)
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/27923
• Institution: Institut Teknologi Bandung

<p align="justify">Source parameters such as slip distribution and slip rate are useful information for understanding the physical processes behind earthquakes. The information can also be used to estimate the impacts that may occur in the area around the source of the earthquake. The isochrone back projection method, or isochrone-BPM, is one method that can be used to obtain slip distribution in the fault plane. Isochrone-BPM incorporates the isochrone concept with back projection method in the determination of slip values in the fault plane. Isochrone-BPM has advantages in its ease of implementation. Nevertheless, in some studies it appears that the results of slip distribution images of isochrone-BPM will always bring up artifacts that cause resulting images to look "blurry". The emergence of these artifacts can result in misinterpretation of the slip distribution, thus becoming a major weakness of isochrone-BPM. <br /> In this research, another approach has been done by using least-squares inversion approach with the addition of damping factor as an alternative of isochrone-BPM. This approach is then referred to as damped isochrone inversion. Damped isochrone inversion can be considered as an alternative method as it still utilizes the core formulation of isochrone-BPM. <br /> The forward modeling and inversion processes have been conducted in this study with the aim to compare the performance of the two methods. Forward modeling is done to obtain synthetic data, which is then processed by both inversion methods. In this study, forward modeling was performed on four cases: normal fault, reverse fault, strike-slip fault, and oblique faults. Forward modeling generates waveform displacement of P, SV, and SH wave phases divided into vertical and radial directions for P and SV waves, and transverse directions for SH waves. <br /> Inversion of synthetic data is done using two methods. The results of isochrone-BPM show that the image quality obtained will depend on the collection of receiving stations used. The isochrone-BPM image quality can turn out to be very bad when information from a number of receiving stations is added. In addition, the isochrone-BPM image will also depend on the focal mechanism of the earthquake, which is indicated by the difference in patterns on different focal mechanisms. The obtained isochrone-BPM images show the “blurry” nature of the isochrone-BPM weakness. Among the three phases used, isochrone-BPM using the SV wave phase has the worst performance. <br /> The resulting image obtained through the damped isochrone inversion does not show any artifacts as shown by the isochrone-BPM image. Contrary to isochrone-BPM, damped isochrone inversion produces slip distribution images that do not depend on the set of receiving stations used. The resulting image of damped isochrone inversion also does not show dependence on focal mechanism. By comparison of the slip distribution imagery results from both methods, it was concluded that damped isochrone inversion has better performance than isochrone-BPM and is excellent for use as an alternative to isochrone-BPM.<p align="justify">