Earthquake-> Landslide-> Tsunami? – oceanbites

Laura Gnesko, Timothy Stahl, Joshu J. Mountjoy, Jonathan M. Carey; Transient proof of shallow coseismic submarine landslides shaping canyon head geomorphology: Insights from the 2016 Kaikōura earthquake, New Zealand. Geology 2025; 53 (12): 1029–1034. doi: https://doi.org/10.1130/G53867.1

Earthquakes!

An earthquake is the sudden shaking of Earth’s floor attributable to the release of built-up vitality within the crust, the arduous, rocky layer we reside on. They often happen when tectonic plates break or slip alongside faults (USGS). Earthquakes vary in magnitude (Mw) from very minor occasions that release little or no vitality (e.g., Mw 3 to 4), to main occasions that release heaps of vitality (e.g., Mw 7 to 10). While earthquakes themselves can do heaps of harm to the floor of our planet and the infrastructure we’ve constructed (Fig.1), they will additionally set off different natural disasters if they’re massive enough and happen in the proper surroundings. Large earthquakes in coastal environments, for instance, run the risk of inflicting landslides that may set off the creation of tsunami waves when the rubble is deposited into the ocean and displaces water.

Landslides!

Landsliding also can occur below water because the consequence of earthquakes, particularly in areas the place there are submarine canyons. Yet, the affect submarine landsliding has on altering the form of the canyons, transferring sediment, and the potential to create a tsunami is poorly understood as a consequence of low decision seafloor information, or the dearth of all of it collectively in some areas.

Gnesko and her group aimed to get a higher thought about how all these items are related by investigating modifications in Kaikōura Canyon after the 2016 Mw 7.8 Kaikōura Earthquake (Fig. 2). On land, the earthquake triggered over 29,000 landsliding occasions, so it was extremely seemingly that there could be submarine landsliding as nicely. However, even with all of the landsliding, no tsunami was generated. The group labored with two units of high-resolution (2 meter) multibeam bathymetry (underwater terrain) information of Kaikōura Canyon – one pre- and one post-quake – to establish variations within the form of the canyon, the place landslides occurred, and how a lot materials was moved in hopes to grasp why such a massive quake was not adopted by a tsunami.

The authors discovered that the canyons, whose tops are 30-40 m beneath sea degree, served as channels for transferring materials away from the cliff faces and out to sea. However, as an alternative of discovering massive rock and particles avalanches like they did on land, the group recognized many smaller landsliding occasions (e.g., slides, flows, falls) from the submarine canyon rims (Fig. 3). These occasions transported almost 100x the fabric of the terrestrial landsliding occasions and brought on the sting of the canyon rim to retreat up to 210 m. When evaluating these findings to decrease decision maps of the identical space, the group was unable to establish these smaller occasions and underestimated how a lot materials had been moved post-earthquake.

Tsunamis?

The group thinks that though these occasions transported more materials than the terrestrial landslides, their smaller dimension finally led to a decrease tsunami hazard potential. Gnesko and her group stress that it’s important to make use of high-resolution mapping information to catch all these small options that seemingly have important implications for the best way materials strikes in a submarine surroundings. If different submarine areas produce these small slides, it’s potential that tsunami hazard potential is definitely a lot decrease in some tectonically lively settings than what was beforehand thought. These findings can be utilized to additional refine tsunami hazard fashions to make sure coastal populations keep secure during these natural disasters.

Cover image from WikiMedia Commons.