Pergerakan tanah berubah bergantung kepada keadaan tanah semasa gempa bumi. Pelbagai kerosakan telah berlaku selepas magnitud 6.0 gempa bumi melanda Ranau dan Kundasang pada 2015. Alat mikrogegaran digunakan untuk mengenalpasti kala pradominan, frekuensi pradominan dan tahap penguatan di 42 tapak kajian di kawasan Kundasang dan Ranau. Peta mikrogegaran untuk kawasan kajian telah dihasilkan. Kerosakan-kerosakan yang diakibatkan oleh gempa bumi Sabah pada 2015 di dalam kawansan kajian telah dikenalpasti, disusun dan didokumentasikan. Berdasarkan sejarah masa pecutan gemba bumi yang telah direkodkan simulasi pecutan permukaan dan spectrum tindak balas dengan kedalaman tanah dengan berbagai-bagai jenis tanah yang sepadan dengan jenis tanah di Ranau dan Kundasang telah dijalankan. Selepas analisis, kala pradominan di kawasan Kundasang ialah antara 0.34 s hingga 0.72 s manakala frekuensi pradominan adalah antara 1.39 Hz hingga 2.92 Hz. Tahap penguatan minimum di Kundasang adalah 1.86 dan 7.75 masing-masing. Di kawasan Ranau, kala pradominan adalah antara 0.25 s hingga 0.57 s manakala frekuensi pradominan adalah antara 1.74 Hz hingga 4.03 Hz. Tahap penguatan di kawasan Ranau ialah antara 1.75 hingga 6.20. Untuk pecutan permukaan tanah dengan pelbagai halaju ricih tanah dan ketebalan tanah, nilai pecutan puncak maksimum ialah 0.52 g pada ketebalan 5 m. Semasa ketebalan tanah meningkat, pecutan permukaan tanah berubah mengikut jenis tanah. Dari ketebalan tanah 0 m ke 8 m, tanah lembut mencecah nilai maksimum. Tanah sederhana mencecah nilai maksimum dalam julat ketebalan tanah 8 m ke 20 m dan 33 m ke 62 m manakala tanah keras mencapai nilai maksimum antara 20 m ke 33 m. Untuk pseudopecutan spectrum sambutan, nilai maksimum iaitu 2.7 g berlaku pada tanah lembut di kala 0.20 s dan ketebalan tanah 5 m. Peningkatan ketebalan tanah mengurangkan nilai pseudopecutan spectrum
_______________________________________________________________________________________________________
Ground motion varies in all location according to the local soil condition. Various damages were observed after a 6.0 magnitude earthquake hit Ranau and Kundasang in 2015. Microtremor instrument was used to measure the predominant period, frequency and amplification level of 42 observation points at Ranau and Kundasang. From here, microzonation maps of the study areas were obtained. The damages occurred after the earthquake within the study areas are identified, compiled and documented. With the recorded acceleration time histories simulations of the ground surface acceleration and response spectrum with different soil types and thickness of soil layer that matches the identified predominant period of soil were carried out. From the results, Kundasang predominant period falls into the range of 0.34 s to 0.72 s while the predominant frequency is in the range of 1.39 Hz to 2.92 Hz. As for the amplification level, it is in the range of 1.86 and 7.75. In Ranau, the predominant periods are in the range of 0.25 s and 0.57 s. As for the predominant frequency, it is between 1.74 Hz to 4.03 Hz. The amplification level in Ranau falls in between 1.75 to 6.20. As for the ground surface acceleration with different soil shear velocity and thickness of soil layer, soft soil reaches the highest surface acceleration which is 0.52 g at 5 m thick in general. However, when the thickness of the soil layer increases, the surface acceleration varies according to soil type. From 0 m to 8 m of soil layer, soft soil has the highest peak acceleration Medium soil has the highest peak acceleration in the range of 8 m to 20 m and 33 m to 62 m thickness of soil while hard soil has the highest peak acceleration from 20 m to 33 m thick of soil. For the pseudo acceleration response spectrum, the maximum pseudo acceleration happens on soft soil which is 2.7 g when the period is 0.20 s at 5 m thickness of soil. When the thickness of soil layer increases, the value of pseudo acceleration decreases.
Structural damage and ground motion characteristics in the 2015 Sabah earthquake / Tan Jun Pin