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Present-day kinematics of Singapore: effects on the reference frame realization

Present-day kinematics of Singapore: effects on the reference frame realization. R.M.S. Fernandes (1) D. Raju (2) V. Khoo (3 ) M.S. Bos (4) W.F.J. Simons (5). ( 1) UBI/IDL (SEGAL), Portugal (2) TMSI, NUS, Singapore (3) SLA, Singapore ( 4 ) CIIMAR, Portugal

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Present-day kinematics of Singapore: effects on the reference frame realization

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  1. Present-day kinematics of Singapore: effects on the reference frame realization R.M.S. Fernandes(1) D. Raju(2) V. Khoo(3) M.S. Bos(4) W.F.J. Simons(5) (1)UBI/IDL (SEGAL), Portugal (2)TMSI, NUS, Singapore (3)SLA, Singapore (4)CIIMAR, Portugal (5)TUDelft, TheNetherlands

  2. Tectonic Settings of S.E. Asia Predicted Tectonic Plate Motions Distribution of Earthquakes (Mw ≥ 5) Sundaland Block USGS/NEIC 1973-2001 DEOS Convergence of Indian, Australian, Philippine and Sundaland plates Thanks to W. Simons and GEO2TECDI

  3. Seismo-Tectonic Context IN/AU/SU Socquet et al. Simons et al. Chamot-Rooke et al. Chamot-Rooke et al. 34mm/yr - 12° INDIA 35mm/yr - 17° SUNDALAND Great Sumatran fault Sunda 53mm/yr - 9° Trench 90°E Ridge AUSTRALIA 67 mm/yr - 15° Plate boundaries Motion Partitioning India Plate collision Thanks to W. Simons and GEO2TECDI

  4. Sundaland Absolute Rotation Vector Thanks to GEO2TECDI

  5. SiReNTSingapore Satellite Positioning Reference Network 0 5 10 15 km SSEK Senoko Ubin Tekong SNYP SSEK SLOY Nanyang Polytechnic Loyang SNTU Nanyang Technological University SKEP Jurong Island Keppel Club Sentosa Southern Islands SSMK Semakau Established in October 2006

  6. Analysis Methodology GIPSY ... Day 1 Day N GIPSY (PPP strategy) GIPSY tools Global parameters (Dedicated Mapping) Solution 1 Solution N Positions of stations w.r.t. ITRF2008 at day 1 Positions of stations w.r.t. ITRF2008 at day N Solution day 1ITRF2008 ... velocity field within ITRF2008 Solution day NITRF2008 Stations

  7. Associated uncertainty estimation • Simple ordinary least-squares will give you already a good estimate of the trend value but a too small error bar because the temporal correlations are ignored. The under-estimation of the error bar can a factor of 5-11 (Mao et al., 1999). • In order to have more realistic error bars we should include this temporal correlation by estimating also the noise properties from the GPS observations. • The power-law + white noise model has proven to represent the noise in GPS data adequately (Williams et al., 2004). White noise – independent observations Power law noise – (temporal) correlated observations

  8. Time-Series (SLOY)

  9. Time-Series (SNTU)

  10. Sumatra Earthquakes 12 Sep 2007 Thanks to USGS

  11. Estimated Coseimic Offsets (SiReNT) -18.8 < East < -16.7 mm -26.0 < North < -23.3 mm -3.9 < Up < +3.0 mm

  12. Time-Series (SLOY)residuals

  13. Time-Series (SSMK)

  14. Velocity Field (w.r.t. ITRF 2008)

  15. Velocity Field (w.r.t. ITRF 2008)comparison with Simons et al. (JGR, 2007) Model based on data observed before 2004 Sumatra EQ

  16. Velocity Field (residuals)comparison with Simons et al. (JGR, 2007) Slower velocity of about 1cm/yr

  17. Internal DeformationSNYP fixed With exception of SSMK, almost all velocities are within the uncertainties (90%)

  18. Vertical Velocity All stations are showing subsidence

  19. Conclusions • The displacement caused by the 12/09/2007 Sumatra Earthquakes are clearly observed on the time-series (up to 32mm). However, the co-seismic signal was almost the same at all the stations not causing significant internal deformation. • SSMK still has a too short time-series to derive any reliable conclusions about its stability. • The estimated velocities are significantly slower (up to 11mm/yr) than the predicted ones using a model based on the velocities before 2004 Sumatra Earthquake, which indicates that the Sundaland tectonic plate has slowed down. • Internally, the internal deformation of the network is smaller than 1.5mm/yr, ensuring that SiReNT is a consistent referential for surveying and other applications. • All SiReNT stations show a consistent pattern of subsidence in the order of 1mm/yr, that probably can be extrapolated for the entire island. Together with sea level rise, this can pose significant risks to the coastal areas of Singapore.

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