Abstract
Abstract. A semi-dynamic datum provides positions with respect to time while taking into account the secular and non-secular deformations, making it the best approach to adapt with the dynamic processes of the earth. Malaysia, as yet, employs a static datum, i.e., GDM2000, at epoch 2000; though Malaysia has evidently been affected by seismic activity for the past decade. Therefore, this paper seeks to propose a design for implementing a semi-dynamic datum for Malaysia. Methodologically, GPS time series analyses are carried out to investigate the seismic activity of Malaysia, which essentially contributes to the proposed design of the semi-dynamic datum for Malaysia. The implications of implementing a semi-dynamic datum for Malaysia are discussed as well. The results indicate that Malaysia undergoes a complex deformation; whereby the earthquakes – primarily the 2004 Sumatra-Andaman, 2005 Nias and 2012 Northern Sumatra earthquakes – have affected the underlying secular velocities of Malaysia. Consequently, from this information, the proposed design, particularly the secular and non-secular deformation models, is described in detail. The proposed semi-dynamic datum comprises a transformation, temporal, and spatial module, and utilizes a bilinear interpolation method. Overall, this paper aims to contribute to the feasibility of a semi-dynamic datum approach for Malaysia.
Highlights
Dynamic processes of the earth are able to displace the land mass of the earth; disrupting any system that requires an ideally non-dynamic platform such as a reference frame
Without clearly exhibiting a post-seismic motion, the 2005 Nias earthquake occurred early in the year causing further displacements. The effect from this shows a post-seismic motion in, especially, the east component: initially heading west, but in 2006 there is a slow change towards east direction and this continued on for the following years, with the Bengkulu earthquake not having much of an impact to the UPMS time series but has a small impact in South Peninsular Malaysia
And table 5, Malaysia undergoes interseismic motion from 2008 to 2011, which can serve as the secular deformation model of Malaysia for a period between 1 June 2005 (~2 months after the 2005 Nias earthquake when the post-seismic effect had reduced) and 1 April 2012 since there are no significant earthquakes that can alter the secular motion during this period
Summary
Dynamic processes of the earth are able to displace the land mass of the earth; disrupting any system that requires an ideally non-dynamic platform such as a reference frame. One major dynamic process would be earthquakes that have proven to cause significant displacements to land mass. As the surface displaces, the reference frame, or essentially a geodetic datum, is affected as well. When reference stations are dislocated in terms of position, the geodetic datum has to shift to accommodate for the dislocation; providing positions that are up-to-date with respect to surface displacements. The International Terrestrial Reference Frame (ITRF) provides a consistent and up-to-date global geodetic datum. The ITRF is updated with regard to the dynamic earth; the ITRF can be essentially called a „dynamic datum‟ (Haasdyk et al, 2014)
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