Northern Indonesia Research Articles

Book Review: Waves of Hope: The U.S. Navy's Response to the Tsunami in Northern Indonesia

Book Review: Waves of Hope: The U.S. Navy's Response to the Tsunami in Northern Indonesia

Sedimentation particularities during the tsunami of December 26, 2004, in northern Indonesia: Simelue Island and the Medan coast of Sumatra Island

Sediments deposited during the tsunami of December 26, 2004, in coastal areas that differ in their structure and orientation relative to the tsunami front are studied with defining of the factors controlling particular features of the sedimentation under different wave intensities. The lithology of tsunami-related deposits and data on various fossils (diatoms, foraminifers, and mollusks) are analyzed. It is established that the tsunami resulted in the accumulation of sediments of various composition, which is explained by the features of the transformation of the wave as well as by the structure of the underwater coastal slope, the flooded zone, and the provenance. Variably oriented coseismic motions are one of the factors influencing the sedimentation patterns. The paleotsunami deposits discovered are compared with their recent counterparts.

COMPARATIVE PHYLOGEOGRAPHY OF THREE CODISTRIBUTED STOMATOPODS: ORIGINS AND TIMING OF REGIONAL LINEAGE DIVERSIFICATION IN THE CORAL TRIANGLE

The Indonesian-Australian Archipelago is the center of the world's marine biodiversity. Although many biogeographers have suggested that this region is a "center of origin," criticism of this theory has focused on the absence of processes promoting lineage diversification in the center. In this study we compare patterns of phylogeographic structure and gene flow in three codistributed, ecologically similar Indo-West Pacific stomatopod (mantis shrimp) species. All three taxa show evidence for limited gene flow across the Maluku Sea with deep genetic breaks between populations from Papua and Northern Indonesia, suggesting that limited water transport across the Maluku Sea may limit larval dispersal and gene flow across this region. All three taxa also show moderate to strong genetic structure between populations from Northern and Southern Indonesia, indicating limited gene flow across the Flores and Java Seas. Despite the similarities in phylogeographic structure, results indicate varied ages of the genetic discontinuities, ranging from the middle Pleistocene to the Pliocene. Concordance of genetic structure across multiple taxa combined with temporal discordance suggests that regional genetic structures have arisen from the action of common physical processes operating over extended time periods. The presence in all three species of both intraspecific genetic structure as well as deeply divergent lineages that likely represent cryptic species suggests that these processes may promote lineage diversification within the Indonesian-Australian Archipelago, providing a potential mechanism for the center of origin. Efforts to conserve biodiversity in the Coral Triangle should work to preserve both existing biodiversity as well as the processes creating the biodiversity.

Field Survey of the 2004 Off-Sumatra Earthquake Tsunami around the Banda Aceh, Northern Sumatra, Indonesia

The 2004 off-Sumatra earthquake (Mw=9.0) was the largest subduction-zone earthquake in the world since the 1964 Alaska earthquake. The 2004 earthquake generated large tsunamis, which propagated across the Indian Ocean and caused the catastrophic disaster. Our international tsunami survey team investigated in the province of Nanggroe Aceh Darussalam, northern Indonesia, in order to clarify the magnitude of tsunami and distribution of tsunami deposits caused by this earthquake.

Weeding through assumptions of livelihood approaches in ICM: Seaweed farming in the Philippines and Indonesia

Seaweed farming is a popular alternative livelihood approach that has been included in Integrated Coastal Management (ICM) projects in many tropical developing countries. Using a comparison of various sites in the southern Philippines and northern Indonesia, this paper examines the assumption that as fishers engage in more lucrative livelihoods, such as seaweed farming, pressure will be reduced on the fisheries. It concludes that in some cases seaweed farming has reduced certain types of fishing activities, but it should not be assumed that seaweed farming alone will result in reduced fishing effort. Appropriately combined with other resource management tools, seaweed farming can contribute to an integrated seascape management approach by providing one component of a diversified household livelihood strategy.

インドネシア第三系西ナトゥナ海堆積盆における圧縮性反転構造運動と石油地質

The West Natuna Sea Basins are the Tertiary, inverted, intra-continental rift-basins in the Sunda Shelf, Northern Indonesia. The basins include remarkable oil producers as well as most other Indonesian Tertiary basins. Inversion-anticlinal traps in the basins have been classic examples of a positive contribution of inversion tectonics to formation of petroleum systems and plays.The Tertiary mega-sequence of the basin includes a Middle to Upper Eocene lacustrine deposit, an Oligocene fluvial to deltaic deposit, an Early Miocene muddy facies deposit, a Middle Miocene deposit of sand-dominant deposit, and a Late Miocene through Recent alternative mud-sand deposit. The West Natuna Sea stratigraphy remarkably lacks the thick Early to Middle Miocene carbonates that are normally well-developed in the most Indonesian Tertiary basins. The Oligocene and Lower Miocene sandstones are productive reservoirs, and widely deposited Oligocene and Lower Miocene mudstones provide regional and top seals, for petroleum systems in the basins.Four petroleum systems are identified in the southern West Natuna Sea based on the magnitudes of inversion tectonics and resulting thermal “kitchen” that developed. Systems (1) and (2) are based on petroleum-charging kitchens, such as the Malay Basin or the Bawal Graben. These kitchens are distinguished from each other by carbon stable isotope ratios of alkanes and aromatics of crude oils and by a biomarker. Systems A and B are by tectonic styles related to petroleum accumulations, such as basement highs or inversion anticlines. The four petroleum system are recognized from west to east and north to south in the area; such as System (1) A (Belida oil field), System (1) B (Tembang, Buntal and Bintang Laut gas pools), System (2) B (Forel oil pool, Belanak oil and gas field) and System (2) A (Udang oil field). System (1) forms much larger petroleum-accumulations than System (2). Sizes of the accumulations are clearly related to the sizes of kitchens that charged the accumulations.

Lateral variations in P velocity and attenuation in the D″ layer, from diffracted P waves

Abstract Diffracted P waves recorded at two stations along the same great circle are analysed to specify the lateral variations in velocity and velocity gradient in the D″ layer at the base of the mantle. Data come from long-period and broadband GEOSCOPE and (GDSN) stations. The variations in both apparent ray parameter and amplitude decay are studied as a function of the dominant period of the P wave. Regional variations in the ray parameter indicate a ±2.5% variation for the P velocity in D′, with high velocities beneath the North Pacific, Central America and northern Asia, and low velocities beneath the South Pacific, South Atlantic and northern Indonesia. The absence of correlation between these velocity variations and the lateral variations in P attenuation favour a chemical origin rather than a thermal origin for these heterogeneities. On the other hand, lateral variations in the velocity gradient are suggested from the frequency dependence of both ray parameter and P-amplitude decay.