A comprehensive assessment of ground motions from two 2016 intra-slab earthquakes in Myanmar

We map the distribution of macroseismic intensities from the M-w 6.9 Kani and the M-w 6.8 Chauk intra-slab earthquakes in 2016 in Myanmar using the 1998 European Macroseismic Scale (EMS-98) by interpreting data gathered from field surveys, community responses sent via social media to the Myanmar Earthquake Committee (MEC), and digital news reports. Our macroseismic maps for both events provide better spatial data coverage in Myanmar, India, and Bangladesh than community derived macroseismic maps (e.g., U.S. Geological Survey's "Did You Feel It?"). In Myanmar, this was driven by improved telecommunication that has allowed social media such as the Burmese language Facebook portal of the Myanmar Earthquake Committee (MEC) to reach into rural areas from where reports of shaking effects from earthquakes have been previously unavailable. Our analysis of both the macroseismic intensities and strong motion observations from India and Myanmar suggests the two earthquakes had different source properties. The comparison of our intensity data with instrumental strong motion records also suggests the peak ground motion-intensity relationship by Worden et al. (2012) generally performs well for both earthquakes. In addition, ground motion behaviour within the Burma and Indian plates can be related to different existing ground motion prediction equations (GMPEs) and intensity prediction equations (IPEs) for subduction zones and for stable continental regions respectively. We therefore suggest these effects will need to be considered in future regional seismic hazard models or Shake Maps for this region when evaluating the impact of the future events.