Felix Tongkul

Universiti of Malaysia Sabah | ums · Faculty of Science and Natural Resources

The region of northern Borneo in South East Asia sits within a post‐subduction setting formed by the recent termination of two sequential but opposed subduction systems. In this study we use seismic data from a recent temporary array deployment to image the crustal velocity structure beneath northern Borneo using a two‐stage Bayesian trans‐dimensio...

Northern Borneo (Sabah) has a complex geological history, having experienced multiple episodes of subduction, magmatism, uplift, subsidence, and extension since the Mesozoic. This includes the subduction of the proto-South China Sea beneath what is now the northwestern margin of Sabah, which terminated ~21 Ma; a postulated later phase of northward...

Subduction termination leads to complex tectonic and geological activity, with the observational record often including clear evidence for exhumation, anomalous magmatism and topographic subsidence, followed by rapid uplift. However, the mechanism(s) driving these responses remain enigmatic and cannot be reconciled with our current understanding of...

This paper presents the significance of a seismic hazard curve plot as a dynamic parameter in estimating earthquake-resistant structures. Various cases of structural damages in Malaysia are due to underestimating earthquake loadings since mostly buildings were designed without seismic loads. Sabah is classified as having low to moderate seismic act...

Studies attempting to gain new insights into the last stage of the subduction cycle are typically challenged by limited direct observations owing to a lack of recent post-subduction settings around the world. Central to unravelling how the subduction cycle ends is an understanding of crust and mantle processes that take place after subduction termi...

The Ranau area is one of the most earthquake-prone areas in Sabah due to the ongoing intraplate deformation in the region. Numerous active faults have been mapped here, but to date these faults are yet to be fully documented in terms of their exact locations and movements. Since 2018, the Department of Mineral and Geoscience (JMG) has installed and...

The relative paucity of recent post‐subduction environments globally has meant that, so far, little is known about tectonic processes that occur during and after subduction termination, as previously convergent tectonic plates adjust to the new stress regime. The region of Southeast Asia that now encompasses northern Borneo has been host to two seq...

Unlike the majority of Malaysia’s other states, Sabah is characterised by frequent seismological activity; on average, an earthquake of moderate magnitude occurs roughly every 20 years, originating primarily from one of two major sources: either a local source or a regional source. Sabah has seen an upsurge in low to moderate seismic activity in re...

Plain Language Summary Northern Borneo lies in the heart of Southeast Asia and was assembled by a complex series of tectonic events over the last 40 million years. Principle among these was the subduction of the Proto South China Sea plate beneath its northwest continental margin, which ended in continent‐continent collision. Subduction of the Cele...

The relative paucity of recent post-subduction environments globally has meant that, so far, little is known about tectonic processes that occur during and after subduction termination, as previously convergent tectonic plates adjust to the new stress regime. The region of Southeast Asia that now encompasses northern Borneo has been host to two seq...

Studies attempting to gain new insights into the last stage of the subduction cycle are typically challenged by limited direct observations owing to a lack of recent post-subduction settings around the world. Central to unravelling how the subduction cycle ends is an understanding of crust and mantle processes that take place after subduction termi...

We use two‐plane‐wave tomography with a dense network of seismic stations across Sabah, northern Borneo, to image the shear wave velocity structure of the crust and upper mantle. Our model is used to estimate crustal thickness and the depth of the lithosphere‐asthenosphere boundary (LAB) beneath the region. Calculated crustal thickness ranges betwe...

Subduction is a key driver of plate tectonics on Earth1. A range of observations indicate that the termination of subduction leads to diverse and unexplained tectonic and geological activity, including anomalous magmatism, exhumation and topographic subsidence, followed by rapid uplift. However, the mechanism driving this complex surface response r...

This paper highlights the level of earthquake hazard in Malaysia, the challenges in mitigating earthquake hazard and the way forward on how to strengthen earthquake science in Malaysia. Earthquake hazard is regarded as low throughout Malaysia, with the exception of Sabah where it is considered moderate. This elevated level of a hazard was reinforce...

Sabah is known for its active earthquake activities, especially in Ranau, Kudat and Lahad Datu areas. The effects of local earthquake can reach M W 6.0. Furthermore, Sabah was also hit by earthquakes from neighbouring countries such as Sulawesi and Philippines. These countries produce highly active earthquakes that can reach as high as M W 8.6. The...

The coastal areas of Sabah are exposed to far-field earthquake-induced tsunamis that could be generated along the trenches of Manila, Negros, Sulu, Cotabato, Sangihe and North Sulawesi. Tsunami simulation models from these trenches indicated that tsunami waves can reach the coast of Sabah between 40 and 120 minutes with tsunami wave heights reachin...

In this paper, we explored the relationship between the stream-length gradient index over the Kiulu River upstream and its respective landform. The knickpoints derived from stream-length gradient index detected sudden drop in elevation that may be associated with recent tectonic activity over NW Sabah. To illustrate the changes in the stream profil...

The seismic hazard analysis requires an estimation of ground motion intensity where the process needs to use a compatible ground motion prediction equation or GMPE, which provides ground acceleration estimates in a function of earthquake magnitude and distance. Hence, the effect of current equation often does not accurately represent the earthquake...

What happens when subduction stops? A team of scientists installed a dense seismic network in Borneo to investigate causes and consequences of subduction termination.

Debris flow remains as a damaging natural hazard in the Crocker Range of Sabah, Malaysia. This is due to the fact that it can move at high velocity and longer travel distance, bringing huge volume of sediment. One of the most severely affected area due to debris flow in the Crocker Range is KM 38.80 of Jalan Penampang-Tambunan in Ulu Moyog, Penampa...

Recurring events of debris flow especially during heavy rainfall have caused cut-off at one of the main road in Bundu Tuhan, Ranau namely Jalan Tamparuli-Ranau KM 83.90. In several incidents, the road was closed to public for hours due to deposition of thick sediment on the road, causing interruption to their daily activities. However, study on the...

The geology in the mountainous area of Sabah western provides a favourable setting for engineering geological instability. The area is underlain by the Trusmadi Formation (Palaeocene to Eocene age), the Crocker Formation (Late Eocene to Early Miocene age) and vary recent Quaternary alluvial materials which are still being deposited. The argillaceou...

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 th...

Debris 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 c...

Flood event is one of the natural disasters that increasingly threaten the safety of the people in an area. Critical infrastructure albeit important, has been shown to be vulnerable to flooding and damages to critical infrastructure element may affect large areas over a longer time period. Critical infrastructures play an important role in function...

This study focused on the engineering geological investigation of slope failures along Penampang to Tambunan road, approximately 12th km to 101th km from Kota Kinabalu city, Sabah, Malaysia. The area is underlain by the Crocker Formation (Late Eocene to Early Miocene age) and the Quaternary Deposits (Recent age). These rock units show numerous line...

Debris flow occurrence is quite common in mountainous areas such as those in the Crocker Range of Sabah, Malaysia especially during prolonged heavy rainfall. While the risk posed by debris flow is enormous, study on its susceptibility level is lacking in Sabah. In the absence of a proper study, the mitigation strategy to address the debris flow haz...

Flooding is one of the major natural disasters in Sabah, Malaysia. Several recent cases of catastrophic flooding were recorded especially in Penampang area, Sabah (e.g. July 1999; October 2010; April 2013; October & December 2014). Heavy monsoon rainfall has triggered floods and caused great damage in Penampang area. The 2014 floods has affected 40...

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 th...

A practical application for landslide susceptibility analysis (LSA) based on Normal Polygon Geotechnical Deterministic Analysis (NPGDA) and GEOSTAtistical INterpolation Techniques (Kriging) (GEOSTAINT-K) for the infinite slope model was used to calculate the factor of safety (FOS) and failure probabilities for the area of Kota Kinabalu, Sabah, Mala...

This study integrates analytical earthquake parameters with tsunami simulation application (TUNAMI-N2) and GIS (Geographic Information System). A total of 350 modelling on six earthquake parameters was carried out and a total of 79 observation segments was used to categorize waves height and to classify the level of tsunami threat in Tawau. Slip ma...

In the recent years, the impacts of floods have gained importance because of the increasing number of people who are affected by its adverse effects. Flood destroyed critical infrastructures that are needed as shelter and also emergency relief for victim. In order to provide a better understanding of flood risk management, a review of current pract...

The aim of this study was to produce Landslide Susceptibility Level (LSL) map for Kota Kinabalu area in Sabah, Malaysia by using both Analytical Hierarchy Process (AHP) and Factor Analysis Model (FAM). Firstly, landslide locations were identified by aerial photographs and satellite images interpretations, field observation and secondary data resour...

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...

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 p...

This study investigates the risk of flood on selected critical infrastructure in a flood-prone catchment in Sabah, Malaysia. Kota Marudu, located in the Bandau floodplain, one of the Sabah's northern water catchments, was selected as the study site due to its frequent flood occurrence and large floodplain coverage. Two of its largest rivers, namely...

An evaluation of the petroleum generating potential of onshore Eocene-Miocene sequences of Western Sabah, Malaysia was performed based on organic petrological and geochemical methods. The sequences analysed are the Belait, Meligan, Temburong and West Crocker formations of western Sabah. The Belait Formation which is Stage IV equivalent in the offsh...

Flooding is one of the major natural disasters in Sabah, Malaysia. Several recent cases of catastrophic flooding were recorded especially in Penampang area, Sabah (e.g. July 1999; October 2010; April 2013; October & December 2014). Heavy monsoon rainfall has triggered floods and caused great damage in Penampang area. The 2014 floods has affected 40...

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, volum...

The Maliau Basin, located in one of the remaining pristine rainforest in Sabah, produces some of the most spectacular waterfalls in Malaysia. The seven-tier Maliau Falls has become one of the major attractions for visitors to the basin. However, other waterfalls within the basin are not well known to visitors and their development rarely publicised...

This study outlines a sedimentological analysis of the Palaeogene West Crocker Formation (WCF) around the Kota Kinabalu area of SW Sabah, which represents a large submarine fan depositional system within part of what was the complex and tectonically active margin of NW Borneo. The newly acquired and often extensive outcrop data summarised in this s...

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...

Traditional management practices have contributed enormously to the world's natural and cultural heritage by creating and maintaining landscapes that sustain the production of multiple goods and services and therefore livelihoods. Traditional forest knowledge is based on long historical experience and deep insight into the dynamics of forest ecosys...

The seismic hazard assessment of a site that lies in the low seismic region affected by the future existence of a large dam has been given less attention in many studies. Moreover, this condition is not addressed directly in the current seismic codes. This paper explains the importance of such information in mitigating the seismic hazard properly....

An outstanding collection of international case studies that provide insight into and suggest best practice for issues such as conservation, risk management, education, marketing, interpretation and technology of actual and developing geotourism sites.

The West Crocker Formation (Oligocene–Early Miocene), NW Borneo, consists of a large (>20 000 km2) submarine fan deposited as part of an accretionary complex. A range of gravity-flow deposits are observed, the most significant of which are mud-poor, massive sandstones interpreted as turbidites and clast-rich, muddy sandstones and sandy mudstones in...

Tanjung Simpang Mengayau, dubbed the "The Tip of Borneo" is one of Sabah's popular tourism sites. The strategic geographical location of this headland is the main attraction for tourist to visit this site. Apart from its beautiful white beach sand, the rocky headland provides an excellent exposure of the lower sandy unit of the Early Miocene Kudat...

Study carried out in the Baliajong River has revealed a hidden trove of rich geological heritage. The river is located about 3 km northeast of Tandek Town in the Kota Marudu District, Northern Sabah. The prominent geological heritage of the area is an ancient oceanic crust of Lower Cretaceous to Paleocene age exposed along the Baliajong River. The...

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Slope failures are frequent occurrences along roads in Malaysia. Not until recently, geological inputs were rarely sought when designing and constructing roads on mountainous areas. This paper highlights the result of a geological study on selected slopes along a major road across Sabah's main mountain range, the Crocker Range, which is comprised m...

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 associ...

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 approximate...

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...