1. Department of Geophysics, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran, Jln. Ir. Soekarno km. 21. Jatinangor, Sumedang 45363, Jawa Barat, Indonesia
2. Postgraduate Physics Program, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran, Jln. Ir. Soekarno km. 21. Jatinangor, Sumedang 45363, Jawa Barat, Indonesia