Did the ground …….

….. move beneath our feet?

As the Congo Canyon instrument recovery has continued and each instrument has returned full of data – multiple movies worth each in fact, which is a quite a large data file to handle for one instrument let alone multiple – we have wondered if any of them recorded the passing by of the large sediment landslide (or turbidite flow) that we know occurred in January, and which broke several submarine telecoms cables crossing the shallower part of the canyon and released all the moorings owned by another group that were deployed into the canyon itself.

Well now we know ……. yes they did.

And not only that, they recorded another flow, not as large but still substantial the following day – the dataset is huge and so we have until now, just looked at the day when we knew a slide occurred – we’ll leave the scientists to plough through all the days these instruments were recording for now that we know they worked as we knew they would.

And here is the evidence measured by one of the ground motion sensors attached to each platform.

This is the output from 5 instruments, where each was deployed at increasing distance along the canyon from top to bottom of the plot.

The large amplitude arrival tracking down the page on the lefthand side, arrives at the nearest instrument at the top of the page first, at abound 12 noon (see time scale at the bottom running horizontally), and then over time, arrives at the next and then the next and the next …… the furthest instrument deployed was nearly 1000 km away from where the flow started – so these flows ready to travel some incredible distance.

We also know how far apart these instruments were, so the speed of flow can also be determined.

The second event that occurred at about 00:00 probably had less material in it, as its signal does not last as long in time.

We wonder how many of these events there will turn out to be?

In between, there are also the training activities to attend, like life boat drills and ……….. fire fighting.

Thankfully a hose like this wasn’t required to get all the mud off our instruments – we used a far gentler approach, although it has taken quite a lot of scrubbing.

 

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