The 2018 Lombok earthquake sequence was controlled by thermal squeezing of the seismogenic zone from an active arc volcano
About the Event:
A sequence of destructive and unusual earthquakes occurred at the volcanic island of Lombok, Indonesia over a 3 week period in 2018. These earthquakes were produced by rupture of the Flores Thrust, which dips beneath the northern coast of Lombok and intersects the root zone of the active arc volcano Gunung Rinjani. The earthquakes are puzzling in a number of ways: two Mw6.9 earthquakes occurred within 2 weeks of each other on the same fault, nucleating near the same point but rupturing in opposite directions. Despite their proximal location and same magnitude, the rupture characteristics of these earthquakes were very different, with the first rupture being significantly rougher than the second. Analysis of a range of seismic and geodetic data, including from a temporary seismic array deployed before the first mainshock, shows that the earthquakes occurred in a narrow seismogenic zone which is elevated and squeezed near the volcano. Seismic data is used to build a 3D geometric fault model which rules out structural variations as the origin of the narrow seismogenic zone. Instead, the primary features of the earthquake sequence are best explained by strong thermal perturbation of the Flores Thrust by the deep magmatic system underlying Rinjani. A simple thermal model can explain many of the observed features and therefore shows that thermal variations in the crust can control fundamental aspects of fault rupture.
About the Speaker:
Karen is a presidential post-doctoral fellow at the Earth Observatory of Singapore, which she joined in November 2018. She is originally from Scotland, obtained a MSci in geophysics from the University of Leeds in 2011, and a PhD from the University of Cambridge in 2015 on the structure and dynamics of Earth’s core. Karen then spent several months travelling before returning to the UK to join a research team at BP, where she developed new seismic techniques and gained experience of industry research. Karen’s research currently applies seismic acquisition technology to a range of topics from fundamental questions about active tectonics and earthquake hazard in SE Asia to urban development in Singapore.