Macro-tidal coral reefs are particularly sensitive to medium to long-term changes in sea-level. Vertical motions of the seabed contribute to both lower or higher relative sea-level changes, particularly in tectonic plate boundary deformation zones along active subduction trenches. Phuket Island in Southern Thailand is subject to both horizontal and vertical land deformations during the seismic cycle of mega thrust earthquakes along the Sumatra and Andaman trenches. The relative sea-level changes in this region were historically monitored using the space geodetic techniques GPS and satellite altimetry alongside the traditional tide-gauge measurements over a period of almost 25 years. The GPS results show that the south of Thailand is still undergoing post-seismic deformations from the 2004 Mw 9.2 Sumatra-Andaman earthquake, after a significant change in the vertical motion of Phuket: from stable quasi-linear uplift at 2.5 ± 0.2 mm/yr, to (temporary) non-linear subsidence rates of 5–10 mm/yr in the past 14 quake aftermath years. The satellite altimetry data estimates the absolute sea-level rise in the Andaman Sea around the island at 3.9 ± 0.5 mm/yr. Therefore relative sea-level changes in Phuket appear to have been slightly positive until the end of 2004, followed by a significant increase averaging ~9 mm/yr that accumulated in 12 ± 1 cm by the end of 2018. Tide-gauge data gives a very similar result. The increased sea-level rise from 2005 onwards, due to tectonic land subsidence, correlates with the enhanced shallow coral reef growth and swift recoveries from bleaching events reported by long-term coral studies in this area.

The existence of intra-plate deformation of the Sundaland platelet along its eastern edge in North Borneo, South-East Asia, makes it an interesting area that still is relatively understudied. In addition, the motion of the coastal area of North-West Borneo is directed toward a frontal fold-and-thrust belt and has been fueling a long debate on the possible geophysical sources behind it. At present this fold-and-thrust belt is not generating significant seismic activity and may also not be entirely active due to a decreasing shelfal extension from south to north. Two sets of Global Positioning System (GPS) data have been used in this study; the first covering a time period from 1999 until 2004 (ending just before the Giant Sumatra–Andaman earthquake) to determine the continuous Sundaland tectonic plate motion, and the second from 2009 until 2011 to investigate the current deformations of North Borneo. Both absolute and relative positioning methods were carried out to investigate horizontal and vertical displacements. Analysis of the GPS results indicates a clear trend of extension along coastal regions of Sarawak and Brunei in North Borneo. On the contrary strain rate tensors in Sabah reveal that only insignificant and inconsistent extension and compression occurs throughout North-West Borneo. Moreover, station velocities and rotation rate tensors on the northern part of North Borneo suggest a clockwise (micro-block) rotation. The first analysis of vertical displacements recorded by GPS in North-West Borneo points to low subsidence rates along the western coastal regions of Sabah and inconsistent trends between the Crocker and Trusmadi mountain ranges. These results have not been able to either confirm or reject the hypothesis that gravity sliding is the main driving force behind the local motions in North Borneo. The ongoing Sundaland–Philippine Sea plate convergence may also still play an active role in the present-day deformation (crustal shortening) in North Borneo and the possible clockwise rotation of the northern part of North Borneo as a micro-block. However, more observations need to be collected to determine if the northern part of North Borneo indeed is (slowly) moving independently.