Two largest marsquakes to date recorded from planet's far side

The seismometer placed on Mars by NASA has recorded two of the largest earthquakes to date. The two events are five times stronger than the previous largest event recorded and are the first recorded events on the planet's far side.

The data from the events could help researchers learn more about the interior layers of Mars.

Anna Horleston of the University of Bristol and colleagues were able to identify reflected PP and SS waves from the magnitude 4.2 event, called S0976a, and locate its origin in the Valles Marineris, a massive canyon network that is one of Mars' most distinguishing geological features. The area had previously been shown to be seismically active, but the new event is the first to be confirmed.

The magnitude 4.1 event recorded 24 days later was characterized by reflected PP and SS waves as well as Pdiff waves, small amplitude waves that have traveled the core-mantle boundary. This is the first time that Pdiff waves have been seen. The location of S 1000a is not certain, but it is similar to S0976a, which originated on Mars. The longest recorded on Mars was 94 minutes, and the energy from S 1000a was the longest.

The core shadow zone is where the marsquakes occurred because P and S waves cannot travel directly to the seismometer. PP and SS waves are reflected at the surface before they travel to the seismometer.

Recording events within the core shadow zone is a real steppingstone for our understanding of Mars. Savas Ceylan, a co-author of the book, said that the majority of the earthquakes were within 40 degrees of InSight.

The two marsquakes are very different. S1000a has a broad spectrum of frequencies and is a clear outlier in our catalog.

The latter event has a frequency spectrum that is similar to a family of events that have been modeled as shallow, crustal earthquakes. Many of the events we have located to the area of extensive faulting that has depths around 50 kilometers are likely to have a similar mechanism.

The two new far-side quakes are outliers compared to the rest of the activity.

Not only are they the largest and most distant events by a considerable margin, S 1000a has a spectrum and duration that is unlike any other event previously observed. Horleston said that they are remarkable events in the Martian catalog.

More information: Anna C. Horleston et al, The Far Side of Mars: Two Distant Marsquakes Detected by InSight, The Seismic Record (2022). DOI: 10.1785/0320220007 Citation: Two largest marsquakes to date recorded from planet's far side (2022, April 23) retrieved 23 April 2022 from https://phys.org/news/2022-04-largest-marsquakes-date-planet-side.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.