Sunday, 5 January 2014

Southern berm of Louisiana sinkhole sagging

An increasing trend of seismic activity at the Bayou Corne sinkhole near Oxy 3 cavern placed the sinkhole staff back on highest level alert late December 2013. Since August 2012 the sinkhole grew from 1 to more than 25 acres (10 hectares / 100 000 square meters).
Images taken on December 23 showed that southern berm developed new cracks where a previous crack was repaired. New cracks were observed in the lowest part of the berm (in a half moon shape). Report from the same day said: "the Micro Seismic Activity (MEQ) has been up for the last few days, with counts as high as 180 MEQ’s yesterday."
In other words, the workers are having hard time maintaining the southern berm.
Increase in seismic activity around Oxy 3 cavern started after burps and trees toppling in August 2013. The area was shaking through September and October, with a brief calm period in November. Another episode of increased activity started on December 14 and is ongoing.
Take a look at images below for Oxy cavern locations and assigned seismic stations. LA 14 station has been particularly interesting, see them all here.

Image credit: LA Dept. of Transportation % Development. Map imagery copyright Google 2013.

Seismic monitor map, October 18, 2013. Map imagery copyright Google 2013.

Picture of the cracks where previous repair was completed. December 23, 2013. Image credit: Assumption Parish Police Jury
Images taken on the morning of December 31 showed the ongoing subsidence of the center portion of the southern berm. 

Subsidence of the center portion of the southern berm. December 31, 2013. Image credit: Assumption Parish Police Jury


Flyover December 18, 2013. Video courtesy AssumptionLA
In August 2013, the sinkhole expanded to as large as 25 acres (10 ha) after swallowing several large trees within seconds.


Video courtesy: Assumption Parish Police Jury
Code Levels - 1 - 3, with Code 1 being the lowest level of alert.
Code 1: Minimal to no seismic activity around/below sinkhole; 10 or fewer of the sharp seismic signals associated with rock movement, called mini-earthquakes (MEQs) or the longer signals associated with gas or liquid movement, called Very Long Periods (VLPs) within 24-hour period; allows work on sinkhole and inside berm area to continue
Code 2: Restricts work directly on the sinkhole, indicates some increased seismic activity around/below sinkhole but not at a level that indicates imminent threat of sloughing or movement below sinkhole (10 to 50 MEQs or VLPs in 24 hours) 
Code 3: Restricts all work inside the containment berm, indicates seismic activity has elevated to a point similar to what has been seen in past monitoring prior to a sloughing on the shore or movement beneath sinkhole (More than 50 MEQs or VLPs in 24 hours)
Read more... About Louisiana sinkhole & timeline of important events at Louisiana sinkhole since May, 2012