Felix Tongkul

Tectonic evolution of Sabah, Malaysia

Abstract Southeastward subduction of oceanic lithosphere in front of the rifted continental block of southern China under an emergent oceanic basement in the eastern part of Sabah controlled the development of an elongate basin trending NE-SW. This basin became the site for the deposition of Middle Eocene-Early Miocene sediments. Active opening of the South China Sea Basin in NW-SE and N-S directions during the Middle Oligocene-Middle Miocene caused further subduction and narrowing of the basin. As a result the Middle Eocene-Early Miocene sediments were compressed into a fold-thrust belt trending approximately NE-SW in the western part of Sabah and NW-SE in the northern and eastern part of Sabah. The subduction was accompanied by volcanic activity in the eastern part of Sabah during the Early-Middle Miocene. The deformed sedimentary pile and underlying oceanic basement were then subjected to a NW-SE extension related to the opening of the Sulu Sea Basin during the Early-Middle Miocene. This resulted in the development of extensive chaotic deposits in the eastern and central part of Sabah. This extension also controlled the development of several circular basins for the deposition of the thick, Early-Late Miocene sediments. Continued extension in this region resulted in further southeastward subduction in southeastern Sabah producing the Late Miocene-Quaternary volcanics.

The geology of Northern Sabah, Malaysia: Its relationship to the opening of the South China Sea Basin

Abstract The northern part of Sabah, consisting of sedimentary and igneous rocks of Early Cretaceous to Pliocene age, has experienced three major episodes of deformation associated with NW-SE and N-S oriented compressions. The earliest episode deformed and uplifted an oceanic basement (Chert-Spilite Formation) to form an elongate basin, trending approximately NE-SW, during the Late Cretaceous to Early Eocene. This elongate basin became the site for the deposition of middle Eocene to Early Miocene quartzose sediments of the Crocker and Kudat formations, sourced from continental basement towards the southwest and north, respectively. These sediments were subsequently deformed by a second episode of deformation associated with NW-SE and N-S oriented compressions, during the latter part of the late Oligocene and the early Middle Miocene, to form a series of imbricate thrust slices. The N-S trending compressive direction controlled the development of approximately E-W trending basins during the deposition of the Upper Miocene sediments of the South Banggi and Bongaya formations. The continuation of N-S compression, which represents the third episode of deformation, gently deformed these sediments. The three episodes of deformation were related to the differential southward movements of continental blocks separated from the southern margin of China during the intermittent opening of the South China Sea subbasins. The first episode was related to the opening of the Southwest Subbasin, while the second episode was related to both the opening of the Southwest and East subbasins. The third episode was related to continued opening in the East Subbasins.

Geological Features for Geotourism in the Western Part of Sahand Volcano, NW Iran

The NW part of Iran is particularly rich in geological features and formations defining its geological heritage, and attracts tourists worldwide. Most of NW Iran is located in a volcanic arc zone of Cenozoic age, including the Quaternary. The subduction of the Neo-Tethys ocean floor beneath the central block of Iran during the Cenozoic resulted in the formation of this zone. This geological setting has provided NW Iran with diverse natural geological features of high significance. Some of the main geological features include the Sahand Volcano, the Urmia Lake, salt deposits, travertine deposits, springs, limestone caves, tectonic structures and Cenozoic vertebrate fossils. This exceptional geodiversity together with the rich cultural heritage provides a valuable base for geotourism and geopark development, which is needed to diversify local economy and strengthen rural development. However, for tourism to be successful and sustainable, the planning and management must be based on up-to-date knowledge and understanding of the tourism resources, as well as on a holistic overview of the many facets of the geological and cultural heritage.

Polyphase deformation in the Telupid area, Sabah,Malaysia

Abstract The Telupid area located in central Sabah consists of Mesozoic ophiolitic basementoverlain by Cretaceous-Oligocene sediments. Detailed mapping of the area has recognised at least three main phases of deformation. The first deformation is characterised by folding and thrusting of basement rock and older Paleogene sediments trending N70E, with associated N-S left lateral horizontal faults. The second deformation is characterised by imbrication of the basement rock and overlying sediments to the NE, with associated NE-SW left lateral horizontal faults. The third deformation is characterised by thrusting of the earlier deformed basement rock and overlying sediments to the NW. The timing of deformation is uncertain, but based on regional consideration they are interpreted to have occurred during the Middle Eocene, early Lower Miocene and early Middle Miocene, respectively, related to major NW-SE compression in the Borneo region.

Quantifying deformation in North Borneo with GPS

The existence of intra-plate deformation of the Sundaland platelet along its eastern edge in North Borneo, South-East Asia, makes it an interesting area that still is relatively understudied. In addition, the motion of the coastal area of North-West Borneo is directed toward a frontal fold-and-thrust belt and has been fueling a long debate on the possible geophysical sources behind it. At present this fold-and-thrust belt is not generating significant seismic activity and may also not be entirely active due to a decreasing shelfal extension from south to north. Two sets of Global Positioning System (GPS) data have been used in this study; the first covering a time period from 1999 until 2004 (ending just before the Giant Sumatra–Andaman earthquake) to determine the continuous Sundaland tectonic plate motion, and the second from 2009 until 2011 to investigate the current deformations of North Borneo. Both absolute and relative positioning methods were carried out to investigate horizontal and vertical displacements. Analysis of the GPS results indicates a clear trend of extension along coastal regions of Sarawak and Brunei in North Borneo. On the contrary strain rate tensors in Sabah reveal that only insignificant and inconsistent extension and compression occurs throughout North-West Borneo. Moreover, station velocities and rotation rate tensors on the northern part of North Borneo suggest a clockwise (micro-block) rotation. The first analysis of vertical displacements recorded by GPS in North-West Borneo points to low subsidence rates along the western coastal regions of Sabah and inconsistent trends between the Crocker and Trusmadi mountain ranges. These results have not been able to either confirm or reject the hypothesis that gravity sliding is the main driving force behind the local motions in North Borneo. The ongoing Sundaland–Philippine Sea plate convergence may also still play an active role in the present-day deformation (crustal shortening) in North Borneo and the possible clockwise rotation of the northern part of North Borneo as a micro-block. However, more observations need to be collected to determine if the northern part of North Borneo indeed is (slowly) moving independently.

The 2015 Mw 6.0 Mt. Kinabalu earthquake: an infrequent fault rupture within the Crocker fault system of East Malaysia

The Mw 6.0 Mt. Kinabalu earthquake of 2015 was a complete (and deadly) surprise, because it occurred well away from the nearest plate boundary in a region of very low historical seismicity. Our seismological, space geodetic, geomorphological, and field investigations show that the earthquake resulted from rupture of a northwest-dipping normal fault that did not reach the surface. Its unilateral rupture was almost directly beneath 4000-m-high Mt. Kinabalu and triggered widespread slope failures on steep mountainous slopes, which included rockfalls that killed 18 hikers. Our seismological and morphotectonic analyses suggest that the rupture occurred on a normal fault that splays upwards off of the previously identified normal Marakau fault. Our mapping of tectonic landforms reveals that these faults are part of a 200-km-long system of normal faults that traverse the eastern side of the Crocker Range, parallel to Sabah’s northwestern coastline. Although the tectonic reason for this active normal fault system remains unclear, the lengths of the longest fault segments suggest that they are capable of generating magnitude 7 earthquakes. Such large earthquakes must occur very rarely, though, given the hitherto undetectable geodetic rates of active tectonic deformation across the region.

RELATIONSHIP BETWEEN RAINFALL AND DEBRIS FLOW OCCURRENCE IN THE CROCKER RANGE OF SABAH, MALAYSIA

flow occurences are quite common in mountainous areas such as those in the Crocker Range of Sabah, Malaysia especially during prolonged heavy rainfall. Despite the recurrence of debris flows in the area, not much information is known about the effect of rainfall on their occurrences. Based on the rainfall intensity-duration of two selected case studies at Jalan Penampang-Tambunan KM38.80 and Jalan Tamparuli-Ranau KM83.90, the debris flow threshold for the Crocker Range cases are approximate to that proposed by Montgomery et al. (2000) given by the equation of I = 9.9D-0.52 which is generally low. This implies that low-intensity rainfall is sufficient to trigger debris flows due to high availability of loose material and weak geological condition.

EARTHQUAKE VULNERABILITY ASSESSMENT (EVAS): ANALYSIS OF ENVIRONMENTAL VULNERABILITY AND SOCIAL VULNERABILITY IN RANAU AREA, SABAH, MALAYSIA

Earthquakes are one of the most common and widely distributed natural risks to life and property. There is a need to identify the possible risk by assessing the vulnerability of the research area. The topic on Earthquake Vulnerability Assessment (EVAs) in Malaysia is very new and received little attention from geoscientists and engineers. Taking the 5.0 Ranau Earthquake 2015 as research study, the research’s main objective was to identify the social vulnerability and environment vulnerability on that area. The framework was formulated semi quantitively through the development of database for risk elements (properties) based on the information from secondary data, literature review and fieldwork. The vulnerability parameter includes social status (injury, fatalities, safety, loss of accommodation and public awareness) and interference of environment (affected period, daily operation and diversity). Each considered parameter in the vulnerability parameter is allocated with certain index value ranges from 0 (0% damage/victims/period),0.25 (1-25% damage/victim/period), 0.50 (26-50% damage/victims/periods), 0.75 (damage/victims/period), and 1.0 (75-100% damage/victim/periods). The value obtained from field work are calculated by using formula and are classified into five classes of vulnerability namely class 1 (0.81): Very High Vulnerability only. Results from this study indicate that a further study is needed to the area of high to very high vulnerability only. This approach is suitable as a guideline for preliminary development in the research area and potentially to be extended with different background and environments.

Landslide Susceptibility Analysis (LSA) using Deterministic Model (Infinite Slope) (DESSISM) in the Kota Kinabalu Area, Sabah, Malaysia

Deterministic slope stability (DSS) infinite slope model (ISM) landslide susceptibility analysis (LSA) failure probability A practical application for landslide susceptibility analysis (LSA) based on two dimensional deterministic slope stability (infinite slope model) (DESSISM) was used to calculate factor of safety (FOS) and failure probabilities for the area of Kota Kinabalu, Sabah. LSA is defined as quantitative or qualitative assessment of the classification, volume (or area) and spatial distribution of landslides which exist or potentially may occur in an area. In this paper, LSA value can be expressed by a FOS, which is the ratio between the forces that make the slope fail and those that prevent the slope from failing. An geotechnical engineering properties data base has been developed on the basis of a series of parameter maps such as effective cohesion (C’), unit weight of soil (), depth of failure surface (Z), height of ground water table (Zw), Zw/Z dimensionless (m), unit weight of water (w), slope surface inclination (β) and effective angle of shearing resistance (). Taking into consideration the cause of the landslide, identified as groundwater change, the maximum groundwater level recorded corresponding to the actual situation of the most recent landslide is considered in this study. The highest probability value of the various scenarios was selected for each pixel and final LSA map were constructed. It has been found from this study that β and Zw parameters have the higher influence on landslide instability. The result validation between the examined LSA map and result of landslide distribution map (LDM) were evaluated. This DESSISM had higher prediction accuracy. The prediction accuracy is 84%. The resulting LSA maps can be used by local administration or developers to locate areas prone to landslide area, determine the land use suitability area and to organize more detailed analysis in the identified “hot spot” areas.