What Makes the Earth Shake?
I have been lucky enough to venture into the world of scientists during my six months of being hosted by Victoria University – learning about “What Makes the Earth Shake.”
Lake Grassmere My first adventure was to visit Lake Grassmere looking for evidence of paleotsunamis in this region. During the field trip I worked alongside Dr. Kate Clark from GNS Science and Dr. Jamie Howarth and his 4 th year geography students. It was real science in action, from gathering data and interpreting data, through to finding evidence and critiquing it for accuracy. The days were cold and chilling to the bone. The job involved strenuous, laborious, repetitive work using a hand auger to lift soil samples from some three metres down and then record meticulously what was found at each layer. I learnt how important this type of work is to inform the public of the need to move to higher ground in quakes lasting over a minute, as there is definitely evidence in this region of three inland tsunami surges here. The oldest tsunami evidence found to date occurred eight hundred years ago, the second three hundred years ago, and the third in the 1800’s.
My next memorable trip was to the Pinnacles, where students studied the lithology of rocks along the Purangirua and Hurupi Streams. The point of the field trip was to identify rock types at predetermined points along the way, find the orientation of tilted strata and look for evidence of submergence and faulting. It was a full days work measuring, drawing, writing and analyzing what was there.
Alpine Fault Seismometers
The Alpine Fault trip was fascinating. I went there to observe and assist a team of three doctorate students whose job was to collect data cards with the latest seismic readings, and to replace batteries, solar panels and other parts. I did get to view the drilling sites where Professor John Townend (my supervisor at Victoria), was involved with the drilling of two major bores down into the fault itself at Whataroa, on the West Coast. John has written a number of interesting papers on the characteristics of the fault, which unlike many other global faults has hot water regions along the fault zone. Unfortunately I did not get to go up on the helicopter, as one or two of the sites up in the alpine area required expert attention. I managed to walk to Franz Joseph and Fox Glaciers instead, which was a plus. I now have some knowledge about how the Alpine Fault works and how deadly powerful it is. Knowing now that the fault is likely to break over a 360 km length or more within the next few decades with an potentially explosive force many, many, times more powerful than the Christchurch quake, is definitely a sobering thought. I have learnt so much in the past six months about ‘What Makes the Earth Shake,” and it has been a huge privilege to work alongside the experts here at Victoria University, thanks to the Royal Society - Te Aparangi.