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Iain's Aerial Surveyor Diary Day 1 2 3

Day One

At last – something I’m really familiar with - earthquake. It’s what I’ve been specialising in as a geologist over the last ten years or so. But even with that the challenge is still daunting. Kate has given Ellen and me the task of finding the epicentre of an earthquake that struck the area in 1872 and to estimate its size on the Richter scale. In strict terms, the first part is impossible – the epicentre of an earthquake is something that is determined by seismic-recording instruments (seismographs) or is inferred from piecing together a picture of where earthquake damage to buildings was greatest. Arriving on the crime scene 130 years later, we’ve got neither of those. A quick plea to the production team – can our task be to simply find the ‘centre’ of the earthquake, which is more vague, rather than the epicentre, which is an impossible holy grail. It is agreed, and though it will still be problematic, Ellen and I start planning.

Now the normal way you’d approach this is to get hold of lots of maps, air photos and satellite images of the area around us to look for the tell tale signs of earthquake. What we’d be looking for are natural straight lines in the landscape, since earthquake cause long cracks, or faults, within the Earth’s crust to rupture and if there’s enough energy available in the quake, the rupture makes it all the way to the ground surface, breaking through as a cliff or scarp. And in our desert landscape these features are often amazingly clear, first because they aren’t eroded away very fast and secondly because the faults are often pathways for water to move up so they appear as areas of moisture on the land surface. That’s where Ellen’s knowledge of vegetation will be great. So in the absence of high-tech images, what we really need to do is get up high and look down on the land. The production team have second guessed us here – they’ve already arranged for a small plane to fly us around if we need it. We do, and we’re off.

Now I don’t normally throw up in planes. And I certainly didn’t plan to chuck up when we’re flying low along an earthquake fault – my dream job. But by the end of two flights I’m face down in a sick bag revisiting my Alabama Hills salad. The trip had started great – from the flat dried flats of Owens Lake we spotted the clear, straight cliff that is so typical of earthquake faults in this region, and we followed it north through Lone Pine and then past Independence. Here it seemed to follow a line of ponds just west of the Owens River. Further north it was even clearer, a high cliff that cut through and displaced small volcanic cones near the town of Big Pine. After that we lost it. Of course, after we spotted the trace of the fault, we had to show it to the camera crew, so up I went again with cameraman Keith and sound recordist Robbie. They’d previously had the pleasure of recording me urinate (programme 1, day 1) but I think that even that was preferable to the sight of me throwing up as the pilot rolled the plane sideways to let Keith get a shot straight down on the fault line. Keith of course missed the action but Robbie, hooked up to me for sound, had no such luck. A very white and sheepish earthquake geologist came off the plane – I think we should stick to looking for this thing on the ground.

Deciding that we should look for where movement on the fault was greatest as the most likely candidate for the centre of the earthquake, Ellen and I jump into the landrover to find where the land surface is most disrupted. This is real detective stuff, because tracking the fault on the ground is much tougher than from the air. The line of pools of water are found almost at the mid-point of the fault (which from our flight we figured was almost 100 kilometres long), but here there was little in the way of direct signs of faulting. The low scarp that runs along one edge of the ponds was probably the fault (it was in the right place) but I was worried that it might also be simply the natural cliffed edge of the Owens River flood plain. We just hoped that in Day 2, things would be much clearer.

There’s another problem. Mike had asked about where to find calcium carbonate and I gave directions to the lovely layered limestone cliffs where we collected the gypsum (and calcite) veins programme 2. But the curse of the limestone appears to be continuing, since Mike tells me that he doesn’t think that its really limestone. Not knowing if he’s collected it from the right point it’s hard to say, but it is possible that the limestone has been baked and chemically changed by heat and pressure, to make what geologists call a metamorphic limestone. So, after a few beers chatting into the night, we head for bed to mull over our various dilemmas.

 

 

The team with the aerial surveyor
Scientists Diaries

See how the rest of the team fared with this challenge:

Ellen
Jonathan
Kathy
Mike