Search

A devastating earthquake with moment magnitude 7.5 occurred in the Noto Peninsula in central Japan on 1 January 2024. We estimate the rupture evolution of this earthquake from teleseismic P‐wave data using the potency‐density tensor inversion method, which provides information on the spatiotemporal slip distribution including fault orientations. The results show a long and quiet initial rupture phase that overlaps with regions of preceding earthquake swarms and associated aseismic deformation. The following three major rupture episodes evolve on segmented, differently oriented faults bounded by the initial rupture region. The irregular initial rupture process followed by the multi‐scale rupture growth is considered to be controlled by the preceding seismic and aseismic processes and the geometric complexity of the fault system. Such a discrete rupture scenario, including the triggering of an isolated fault rupture, adds critical inputs on the assessment of strong ground motion and associated damages for future earthquakes. Plain Language Summary: On 1 January 2024, a moment magnitude 7.5 earthquake occurred in the northern Noto Peninsula, Japan. The strong ground motion and tsunami associated with the earthquake caused severe damage to buildings and infrastructure, resulting in at least 245 causalities in the affected areas. The Noto Peninsula is affected by northwest‐southeast compression, and active reverse faults are known along the northern coast of the peninsula and its offshore region. Before the 2024 earthquake, the source region experienced long‐lasting earthquake swarm activity, which is a set of seismic events without an obvious mainshock‐aftershock pattern. Our seismological analysis found that there was a 10‐s‐long initial rupture episode around the hypocenter that overlapped with the earthquake swarm region. The initial rupture was followed by a series of three different rupture episodes on differently oriented fault segments. This earthquake highlights a multi‐scale rupture growth across a segmented fault network after a very quiet initial rupture process that was controlled by the preceding earthquake swarms and associated aseismic deformation related to fluid injection from depth. The rupture process advances our understanding of earthquake source physics and can lead to a better assessment of future earthquake hazards. Key Points: The 2024 Mw 7.5 Noto Peninsula earthquake involves a multi‐segmented rupture sequence on differently oriented faultsThe long and quiet initial rupture domain coincides with the preceding earthquake swarm regionFluid‐induced earthquake swarms and a segmented fault network control the complex earthquake rupture growth [ABSTRACT FROM AUTHOR]

Kim, K.O., Choi, B.H., Pelinovsky, E. and Jung, K.T., 2013. Three-dimensional simulation of 2011 East Japan-off Pacific coast earthquake tsunami induced vortex flows in the Oarai port. The huge tsunami was generated by the 11 March 2011 off coast of the Pacific side of East Japan, recording a maximum 40 meter run up in Iwate prefecture. The tsunami wave attacked the Oarai port of Ibaraki prefecture within 30 minutes, and created an enormous vortex flow within the harbor. A similar feature was observed in the Imwon port, in the Eastern Korean coast during the 1983 tsunami event in the East (Japan) Sea. A set of simulations have been performed to investigate the generation of the powerful vortex caused by the 2011 tsunami event at the Oarai Port. The application of numerical models has successfully reproduced the formation of the vortex in the center of the port, which can be clearly identified in a photograph taken during the tsunami. The simulation of tsunami generation and propagation at the outer sea is performed with a hydrostatic model and, for the investigation of a more detailed transient pattern of water flows, the model which uses full Reynolds-averaged Navier-Stokes equations is applied. Examination of the Oarai and Imwon vortexes implies that the generation and strength of a vortex due to tsunami wave is strongly related in the size and the shape of port and breakwater layouts. The present work indicates that time-variation the inflow through the mouth of a harbor controls the transient pattern of the vortex. [ABSTRACT FROM AUTHOR]