Calendar

December 2018

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Seminar
Revisited Mantle Structure beneath the Sunda Arc

Revisited Mantle Structure beneath the Sunda Arc

Seminar
Speaker: Sri Widiyantoro
Date: Fri, 2018-12-07 16:00 to 17:00
Venue: ASE 3D Visualisation Laboratory (N2-B1c-16c)

About the Event

Detailed P-wave velocity structure beneath the Sunda arc has been successfully imaged by applying a non-linear approach to seismic tomography and using the new data provided by the 2004–2005 Sumatra-Andaman great earthquake sequences. Nearly one million compressional phases from events within the Indonesian region have been used. These include the surface-reflected depth phasespP and pwP in order to improve the sampling of the upper-mantle structure, particularly below the back-arc regions. We have combined a high-resolution regional inversion with a low-resolution global inversion to minimize the mapping of distant aspherical mantle structure into the study region. The tomographic images indicate thatthe slab is folded at depth beneath northern Sumatra, exhibiting geometry similar to that of the volcanic arc and the trench at the surface. We envisagethat this fold plays a major role in the segmentation of the Sumatra megathrust, and may impede rupture propagation in the region. North of Andaman, significant slab material in the mantle transition zone is imaged for the first time, and we infer the presence of a major tear between the upper mantle and transition zone there. East of Sumatra, the tomograms depicta hole in the subducted slab in the upper mantle beneath eastern Java and suggest that a tear in the slab exists below the easternmost part of the Sunda arc, where the down-going slab is deflected in the mantle transition zone. In good agreement with previous studies, the properties of the deflected slab show a strong bulk-sound signature.In addition, we also observe a southward dipping feature below Bali depicted clearly by P- and S-wave images derived using similar ray path coverage. This feature is intriguing and in excellent agreement with local seismicity. The south-dipping feature in the back-arc region to the north of Bali has caused some tsunamigenic events. Following the great Andaman–Sumatran earthquake of 26 December 2004 with its attendant devastating tsunami, there have been calls for a tsunami early warning system for the Indian Ocean. Inferences from this study also urgently call for such an early warning system to mitigate tsunami hazards not only in the fore-arc, but also in the back-arc regions of Bali and small islands to the east.



Sri Widiyantoro

Sri Widiyantoro is a professor of seismology at ITB, Bandung, Indonesia, where he has spent his academic career since 1987. He has frequently conducted research and study visits at prestigious universities overseas, including MIT and ANU, where he finished his Ph.D. program, and research institutions (e.g. Earthquake Research Institute, Tokyo University) to work with top scientists on collaborative research. His main research interest is in the field of seismology, particularly seismic tomographic imaging. His tomographic models have been published in various journals, including top journals like Science and Nature. Alongside his work on large-scale seismological problems, he has engaged actively in consultancy on oil, gas, and geothermal explorations related work in Indonesia, so that he can bring a very broad perspective to his science.

He has received recognition through many awards including the Doornbos Memorial Prize from the IUGG Committee on the Study of the Earth’s Deep Interior, the Habibie Award from the Habibie Center, the Science and Technology Award from the Indonesian Toray Science Foundation, and the Australian Alumni Award for Research and Innovation. He has been a Fellow of the Indonesian Academy of Sciences since 2011. He is currently Dean of Faculty of Mining and Petroleum Engineering, ITB, and was the President for the Indonesian Association of Geophysicists (2012-2014). Since 2015, he has been the Head of the Seismology Working Group of the National Center for Earthquake Study (PuSGeN) for updating the Indonesian seismic hazard maps that were published in 2017.


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Sri Widiyantoro
16:00 to 17:00
 
 
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Conference 2018 American Geophysical Union Fall Meeting

2018 American Geophysical Union Fall Meeting

Conference

Date: Mon, 2018-12-10 08:00 to Fri, 2018-12-14 18:30
Venue: Walter E. Washington Convention Center

About the Event

This year's Fall Meeting marks the American Geophysical Union's Centennial, and is the first time the Meeting is held in Washington, D.C.

The Earth Observatory of Singapore and the Asian School of the Environment are represented at AGU by 41 researchers giving a total of 45 presentations. Associate Professor Nathalie Goodkin and PhD student Molly Moynihan will also be hosting a town hall on Thursday 13 December. Please click on the attachment below to view the presentation schedule.

The Community Engagement Office will also be leading outreach efforts at booth 1543 in the exhibition hall.

 




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08:00 to 18:30
 
 
 
 
Seminar
Cross-latitudinal climate teleconnections for the last 250 ky: greening the path for human migrations out of Africa

Cross-latitudinal climate teleconnections for the last 250 ky: greening the path for human migrations out of Africa

Seminar
Speaker: Nicolas Waldmann
Date: Tue, 2018-12-11 16:00 to 17:00
Venue: ASE 3D Visualisation Laboratory (N2-B1c-16c)

About the Event

Studying the geographical variability and structure of past climate change is critical for understanding the mechanisms behind external climate forcing and how these are translated into regional environmental adaptability. This becomes even more crucial for regions that are highly susceptible to climate change, such as those bordering hyper arid environments. Sub-tropical Africa underwent millennial-scale latitudinal migrations of the ITCZ, which in turn leaded to enhanced humidity during intervals of insolation maxima. In the current presentation, well-constrained lacustrine sedimentary records from both equatorial and sub-tropical regions (Lake Chala (Kilimanjaro area) and Dead Sea, respectively) are used to provide valuable information on cross-latitudinal climate teleconnections during the last 250 ky. This is especially important for understanding how the environmental and climate conditions related to periods with increased monsoonal activity allowed (or inhibited) early human migration out of Africa.



Nicolas Waldmann

Dr. Nicolas Waldmann is from the Department of Marine Geosciences, University of Haifa. He is a geologist majoring in limnogeology and marine geology, with emphasis of using these sedimentary records for climate change reconstruction and basin processes. He has obtained his MSc from the Hebrew University of Jerusalem (Israel), then a PhD at the University of Geneva (Switzerland) and completed a postdoctoral research at the University of Bergen (Norway). Upon his return to Israel in 2011, he founded the Basin Analysis and Petrophysical laboratory (PetroLab) at the University of Haifa, which currently hosts a group of 4 postdocs, 5 PhD and several MSc students. The research is carried out in several places in the world, including Kenya, Chad, Mali, China, Norway, Malta, Oregon, Chile, and Yemen. Based on academic excellence and achievements, he was awarded with the Krill Prize of the Wolf Foundation in 2013.


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Nicolas Waldmann
16:00 to 17:00
 
 
 
 
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