# Spatio-Temporal Distribution of Ground Deformation Due to 2018 Lombok Earthquake Series
## 4 Discussion  
Lombok earthquake series in 2018 contains four main events (29 July, 5 August, 9 August, and 19 August 2018) and at least 818 minor earthquakes in between these dates until 31 August 2018. This study emphasizes the displacement following each principal earthquake at the northern part of Lombok Island based on the DInSAR technique. The interferograms allow us to describe the pattern of displacement. The spatial distribution of vertical displacement in raster format helps to measure the value of uplift and subsidence in meters. Each earthquake has different impacts on the displacement in Lombok Island. The first 6.4 Mw foreshock hitting on 29 July 2018 produces a minimum uplift effect on the island. However, it causes deep subsidences in the northwest area and on the Rinjani volcanic complex. The 7.0 Mw mainshock on 5 August 2018 causes an extreme uplift at the northern shore. The 6.2 Mw Aftershock on 9 August 2018 generates subsidence throughout the study area. The final earthquake of 6.9 Mw on 19 August 2018 initiates a massive uplift in the study area and an extreme uplift at the northeastern shore. These could be caused by two reasons. Firstly, limited distance between Back Arc Thrust and the Lombok island produces greater deformation impacts at the northern shore (Figure 2). Secondly, the epicenters are continuously changing between these four major earthquakes indicating unstable tectonic setting beneath the island due to brittle damage in the Earth's crust. Fortunately, there is no report on increasing volcanic activity. This confirms that there is no reciprocal relationship between volcanism and earthquake series [58]. Most of the displacements that can be measured with good coherency are located next to the shoreline. Therefore, we conduct observation at 6 selected areas: Mataram City, Pamenang, Tampes, Sukadana, Sembalun, and Belanting. The highest uplift reaches 0.713 m  
Figure 6: Summary of displacement after each earthquake in selected areas (Mataram city, Pamenang, Tampes, Sukadana, Sembalun, and Belanting). at Tampes due to the mainshock earthquake of 7.0 Mw on 5 August 2018, while the deepest subsidence is measured \(-\)0.338 m at Pamenang following the aftershock earthquake of 6.2 Mw on 9 August 2018 (Table 2). Mataram city has the modest displacement since it is located far from epicentrum. Rapid assessment after event conducted by _Pusat Gempa National_ (Indonesian National Center for Earthquake studies) has revealed microatoll coral at northeastern part of the island [1] corresponding to an average uplift of 0.265 m in Belanting due to an earthquake of 6.9 Mw on 19 August 2018 that is measured in this study. Liquefaction is s also found at the subsidence area in Pamenang following the aftershock earthquake of 6.2 Mw on 9 August 2018 [1]. In the field, the deformation could also be corresponded to 4823 landslides after the earthquake on 5 August 2018 and 9319 landslides after the earthquake on 19 August 2018 [59] as well as small scale tsunamis following this earthquake series [60]. Dominant deformation at the northern area of Lombok Island indicates movement of Back Arc Trust in the north of the island [61]. The pattern and value of deformation in this research are similar to previous DInSAR research in the Lombok area, especially for earthquake on 5 August 2018 [4,52] and earthquake on 19 August 2018 [1,62]. However, earthquake on 29 July 2018 between this research and previous study [1] has shown different results because of the different master and slave images. This study applies radar images on 27 July 2018 (master) and on 2 August 2018,