Nature Is Its Own Secretary
Coverage of the Haiti earthquake from January 12th is everywhere. My weekly morning is spent creating the news for Spokane’s local CBS affiliate. I receive a daily dosage of news at an average of two to three hours a day. An interesting question sparked in the control room during the newscast concerning the history of Haiti’s seismic activty. The Haiti earthquake is the biggest seismic occurance in that region in over 200 years. How do we know this?
Today we’ll talk about the possibilities of technology created over the years by the human race and what exactly it can do for us. Not modern technology, but instead, let’s begin to the days of Aristotle, the original reinassance man (during the classical period).
According to the U.S. Geological Survey, “It was recognized as early as 350 BC by the Greek scientist Aristotle that soft ground shakes more than hard rock in an earthquake.”. Later descriptions sprouted over time, but his was the first scientific description besides the idea that angry animals were pounding on their earth with all their might.
Biological creatures since the dawn of time have felt the earth move under their feet. The first recorded mention of this natural phenomenon was from China in 1831 BC. From there, crude contraptions to record and document the events were devised, mostly from Chinese minds. It’s not truly known if the Chang Heng’s seismoscope truly existed. Myth busters of the nineteenth and twentieth centuries debated this device and no conclusion was ever drawn. If the original Chinese seismoscope did exist it would have determined the direction of the earthquake within a 400 mile radius.
Over the years, more ingenious devices were invented becoming more scientific to factually detail the seismic activity. The recording of this date is nothing new to history and is something that has been suggested and around for almost 2,000 years. More advanced seismic instruments started popping up around Europe in the 18th century and from there we now have our modern seismograph stations all around the world and based off of the Wiechert inverted-pendulum seismometer. In most cases, these devices are digital and are available in real time. You can read about the history of seismic recorders at the U.S. Geological Survey’s website which provides a treasure trove of knowledge. My way of spending a Wednesday night.
Even though our ability to record history is impressive, we must not forget an original and rather unorthodox method. The natural method. For this, we turn to nature.
Dendrochronology, is the study of tree-rings coined in the early 1900s by A. E. Douglass, an astronomer. From the stories imprinted in the life of a tree, you can learn its experiences. Everything from droughts, fires, sun-spots and most important to today’s conversation: earthquakes. Evidence of this can be found by studying dead red-cedars of the Pacific Northwest and discovering evidence of the Cascadia Earthquake of 1700.
How does this tie to Haiti? The one thing Haiti lacks currently is old growth forest. Or at least growth old enough to demostrate evidence of 200 year old earthquake. 1954 marked a major deforestation effort in order to sustain the need for resources. By 1988, only 2% of the island of Haiti had forest coverage. The trick is finding a tree or at least a remanant of a tree old enough to show evidence of these events. Once this is accomplished, you can determine the event type and the stress on the tree.
To manually record seismic activity 200-years ago, a common instrument used during that time period might have been somewhere between Duca della Torre’s sismografo and James Forbes’s seismometer.
I personally can’t truly determine the capacity of these methods nor the full impact of the earthquake 200 years ago. What I can provide is simple research to deduce the how to the question. How did we know that this is the biggest earthquake in that region in 200 years? Easy. Science!