Source reconstruction of the 1969 Sulawesi, Indonesia earthquake and tsunami

<p>An M7.0 earthquake followed by moderate tsunami destructed Majene region, western Sulawesi on 23 February 1969. This event claimed at least 64 lives and caused severe damage to infrastructure. In this study, we reconstructed the earthquake and tsunami source of this event by optimising macroseismic and tsunami dataset reported as well as analysed the earthquake focal mechanism. We estimated that the maximum intensity of the earthquake was VIII (in Modified Mercalli Intensity). From the first motion polarity analysis, the earthquake had a thrust mechanism which was plausibly from the Makassar Thrust. Further, deterministic ground motion modelling successfully fits the intensity data. However, thrust earthquake from the Makassar Thrust was unable to reconstruct 4 m tsunami height observed at Pelattoang. The estimated ratio between maximum tsunami run-up height and lateral distribution distance (<em>I<sub>2</sub></em>) from the dataset indicates that the tsunami was generated by a local coastal landslide.</p><p>(This study is funded by the Royal Society (UK) grant number CHL/R1/180173)</p>

Risk Oriented Earthquake Hazard Assessment: Influence of Spatial Discretisation and Non-ergodic Ground-Motion Models

Three important aspects of ground-motion modelling for regional or portfolio risk analyses are discussed. The first issue is the treatment of discretisation of continuous ground-motion fields for generating spatially correlated discrete fields. Shortcomings of the present approach in which correlation models based upon point estimates of ground motions are used to represent correlations within and between spatial regions are highlighted. It is shown that risk results will be dependent upon the chosen spatial resolution if the effects of discretisation are not adequately treated. Two aspects of non-ergodic groundmotion modelling are then discussed. Correlation models generally used within risk modelling are traditionally based upon very simple partitioning of ground-motion residuals. As regional risk analyses move to non-ergodic applications where systematic site effects are considered, these correlation models (both inter-period and spatial models) need to be revised. The nature of these revisions are shown herein. Finally, evidence for significantly reduced between-event variability within earthquake sequences is presented. The ability to progressively constrain location and sequence-dependent systematic offsets from ergodic models as earthquake sequences develop can have significant implications for aftershock risk assessments.

Strong ground motion observations of engineering interest from the 14 November 2016 Mw7.8 Kaikōura, New Zealand earthquake

This paper provides a brief discussion of observed strong ground motions from the 14 November 2016 Mw7.8 Kaikōura earthquake. Specific attention is given to examining observations in the near-source region where several ground motions exceeding 1.0g horizontal are recorded, as well as up to 2.7g in the vertical direction at one location. Ground motion response spectra in the near-source, North Canterbury, Marlborough and Wellington regions are also examined and compared with design levels. Observed spectral amplitudes are also compared with predictions from empirical and physics-based ground motion modelling.