Comparison of Arabian plate motion using satellite laser ranging and GPS observations A.O. Alothman 1 , S. Schillak 2 , R.M. Fernandes 3 1: King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia(aalothman@kacst.edu.sa) 2: Space Research Centre, Polish Academy of Sciences, Astrogeodynamic Observatory, Borowiec, ul. Drapalka 4, 62-035 Kornik, Poland, sch@cbk.poznan.pl 3: SEGAL (UBI/IDL), Covilhã, Portugal (rmanuel@di.ubi.pt) AGU FALL MEETING San Francisco, 9-13 December 2013 1. Abstract Two different space based observations have been used to estimate the velocity of the Arabian plate motion. The first set of observations is using the Saudi Arabia Laser Ranging Observatory (SALRO - 7832), which is situated in the middle of Arabian tectonic plate. Satellite Laser Ranging (SLR) observations of about 20 global SLR stations to LAGEOS-1 and LAGEOS-2 satellites collected for 14 years (1996-2009) have been used to determine Riyadh SLR station positions. The NASA Godard's GEODYN-II orbital software has been used to perform orbit determination of these two satellites. The velocities were computed in reference to the ITRF2008 terrestrial reference frame; 29.1 mm/yr, 31.6 mm/yr, and 1.9 mm/ yr in North, East and vertical directions, respectively. The second set of observations consists of Global Positioning System (GPS) observations of 22 GPS stations acquired in campaign and continuous mode for the period 2003 to 2009. having at least 2.5 years’ time span. Multi-year processing of stations having at least 2.5 years’ time span and excluding stations within the deformation zone of Red Sea Ridge, such that they are distributed evenly within the rigid (interior) part of the Arabian plate. The Bernese 5.0/ADNEQ2 and GIPSY-OASIS II software was used to compute the daily solutions of coordinate time series implementing the Precise Point Positioning (PPP). The velocities were estimated in the ITRF 2008 and the average velocities were 28.2 mm/yr, 32.4 mm/yr, and 1.0 mm/yr in North, East and vertical directions, respectively. Comparison of the results shown that the Arabian tectonic plate motion determined from Riyadh SLR data and GPS campaigns are in a good agreement with the recent estimates; global geodetic model GEODVEL and geophysical MORVEL model. 2. Background 3. Arabian Plate Angular Velocity 4.Comparison between the models Acknowledgement: King Abdulaziz City for Science and Technology, KACST, for the support to publish this paper. General Directorate of Survey, GDMS, is acknowledged for providing the data .This work has been partially supported by Polish fi nancial resources for science in 2010-2013 as a research project No. N N526 231839 . References  A. O. Alothman, S. Schillak, Recent Results for the Arabian Plate Motion Using Satellite Laser Ranging Observations of Riyadh SLR Station to LAGEOS-1 and LAGEOS-2 Satellites. Arab J. Sci. Eng., 01 November 2013, DOI 10.1007/s13369-013-0823-7. -  http://neic.usgs.gov. . http://www.globalcmt.org. - Rui M S Fernandes, Fredrique Rolandone, Sylvie, Abdulaziz Alothman, Ahmed Al-Aydrus, Hassan Khalil, Abdulkarim Ahmed, K. Khanbari, Machiel S Bos, Philippe Nicolon, Laurent Heydel, The opening of the Aden Gulf Ridge Derived from GPS Con straints and Plate Tectonic Models. AGU Fall Meeting, San Francisco, 3-7 December 2012. - R.M.S. Fernandes, F. Rolandone, S. Leroy, A. Alothman , A. Aydrus, I. El-Hussain, H. Khalil , A. Ahmed, K. Khanbari, M. Bos , P. Nicolon , L. Heydel, - R.M.S. Fernandes, et. al., Evaluation of the Current Opening of the Arabia-Somalia Plate using Space-Geodetic Data. The 8th Gulf Seismic Forum, GSF 2013, Muscat, Oman. - Argus et. al., The angular velocities of the plates and the velocity of Earth's centre from space geodesy, Geophys. J. Int. (2010) 180 (3): 913-960. doi: 10.1111/j.1365-246X.2009.04463.x . - DeMets, C., Gordon, R., and Argus, D., Geologically current plate motions, Geophysical Journal International, Vol. 181, 1, 1-80, 2010:DOI: 10.1111/j.1365-246X.2009.04491.x . 5. Conclusions 1. The SLR and GPS velocity solutions at SALRO are at sub -millimeter level showing the consistency between these techniques. 2. The recent global tectonic models show predictions that differ at cm/yr level - therefore, the need to improve them by computing a dedicated model still exists. Table 1. GPS stations used in the study. Document # 19P0017-PST-0001-ER01 Figure 1. Arabia (ARAB) Tectonic Plate Boundaries. Dark circles are events with magni- tude higher than 2.0 .Red circles of magnitude higher than 5.0 . Site Name Initial Final. Years No. of Days DATM 2005 2009 CAMPAIGN - P005 2005 2009 CAMPAIGN - P013 2005 2009 CAMPAIGN - P016 2005 2009 CAMPAIGN - P024 2005 2009 CAMPAIGN - P035 2005 2009 CAMPAIGN - P042 2005 2009 CAMPAIGN - JEDD 2004 2009 6.0 560 JIZN 2007 2010 3.9 1440 BHR1 2000 2011 10.3 3512 FG31 2007 2012 3.7 1058 FG40 2009 2012 3.7 1055 HALY 2002 2013 10.9 1256 KUWT 2006 2013 6.9 2449 NAMA 2004 2012 7.7 1856 SALP 2008 2012 3.4 888 SOLA 2004 2012 8.7 1341 YIBL 2003 2013 10.3 3014 YRS1 2009 2012 3.6 1016 Figure 1 shows the seismicity around the Arabia plate which clearly identifies the boundaries with other tecton- ic units. Dark circles are events with magnitude higher than 2.0 extracted from the NEIC catalog (http:// neic.usgs.gov). Centroid Moment Tensors for events since 1976 with magnitude higher than 5.0 are also shown (http://www.globalcmt.org). It is observed that the high seismic regions are the northeastern part (wide de- forming area in contact with Eurasia) and the southern part – border with Somalia (Aden Gulf Ridge). The sta- ble Arabia is countering some compression occurring in- side the plate caused by the pushing due to the opening of the Nubia-Arabia (Red Sea) plate boundary (Fernandes, et. al., 2013). The border with the Indian plate is less prone to large seismic events due to the slower opening rate between these plates. GPS observations were acquired in campaign and continuous mode. Daily solutions were computed with the GIPSY - OASIS II and Bernese 5. software package using the PPP - Precise Point Positioning strategy with ambiguity resolu- tion. Velocities and associated uncertainties were computed using hector (http://segal.ubi.pt/hector/) which take into ac- count the temporal correlations (colored noise) on the time -series. This approach has significant advantages when there are a significant number of data gaps in the time -series, which is the case for several stations in the processed network. Table 1 shows 22 secular motions that were used to compute the angular velocity for the Arabia plate. The stations with short time-series (less than 2.5 years), were excluded. We compare the predicted relative motions of the Arabian plate as given by three different models, two based on geodetic observations (this study, and GEODVEL) and one based on geophysical and geological data (MORVEL). Absolute mo- tion of the Arabian plate has been estimated earlier using SLR (Alothman and Schillak, 2013) and used here for compari- son, see Figure 2. Riyadh observations to LAGEOS-1 AND LAGEOS-2 Satellites SLR of about 14 years span have been used to compute the station velocities using GEODYN_II software. Table 2 shows the velocities at SALRO and SOLA which are having similar motions in the East and North components(0.1 and 0.2mm/yr, respectively). The Vertical compo- nent, as expected, shows a larger difference (3mm/yr) which we attribute to the different way how the seasonal signals were taken into account.. Comparison has shown that the Arabian tectonic plate motion determined from Riyadh SLR data and GPS campaigns are in a good agreement with the global geodetic model GEODVEL and geophysical MORVEL mod- el. We used the location of the CORS stations (see Table 1) to compare the predictions given by the three considered plate models. Table 3 shows major statistics for the differences between the predicted motions. Site Name Vel. E mm/y Vel. N mm/y Vel. U mm/y SOLA 31.5 28.9 -0.9 SALRO 31.6 29.1 1.9 Table 2. Velocities at SOLA & SALRO. Model Pair Min. mm/y Max. mm/y R.m.s. mm/y GEODVEL-This study 1.1 5.8 4.1 MORVEL-This study 4.6 6.8 5.4 GEODVEL-MORVEL 4.6 11.0 7.9 Table 3. Major statistics for the differences between the predicted motions. Figure 2; Comparison between models. Red arrows; MORVEL, Green arrows; GEODVEL, Black arrow; SLR, and Yellow arrows; GPS (this study). View publication stats View publication stats