Where did that Earthquake Come From?

Posted by Hans de Ruiter

New Zealand is on the Pacific rim of fire, and so has volcanos and periodically experiences earthquakes. This geological activity has shaped the stunning scenery that New Zealanders (and visitors to the country) enjoy. It also occasionally makes you jump when a strongish earthquake hits the local area, as happened recently. Eruptions of molten lava, ash, or just boiling mud happen once every several years, which can close airports due to the danger of fine ash clogging up the jet engines.

Some people living in countries without earthquakes and volcanos may wonder if we live in fear of "the big one.; after all, New Zealand experiences over 15,000 earthquakes a year of which 250 are seen as significant. I cannot speak for all New Zealanders, but I think that, while the country is prepared for a large earthquake, most people do not think about it. If anything, when someone notices an earthquake, the first instinct for others is to sit down so that they too can feel it (people standing or moving usually do not notice). Door posts and areas under tables are sought out only if the shaking becomes serious, and most earthquakes are over before anyone manages to take a step toward the door. It is also important to remember that buildings in New Zealand are designed to withstand large earthquakes.

The scientist in me still has not lost that child-like desire to know the whys, wheres and hows of everything. Thus, when an earthquake is felt, I am always curious as to how big it was and where it was centred. I recently discovered that GeoNet's website provides near real-time data about seismic activity in New Zealand. It was from this website that I discovered that one earthquake was centred just over a kilometre from where I was at the time, ignoring the earthquake's depth, which was kilometres below the surface. Being that close, it did have more of an upward jolt to it as opposed to the usual sideward rocking motion.

Other interesting items that I noticed whilst scanning the GeoNet website is that Mt. Ruapehu and White Island are both on level one (out of five) on the volcano alert scale. These two volcanos are typically the most active in the country. Hopefully Mt Ruapehu will remain at that level and not erupt, or it will ruin the ski season for the two ski fields on that mountain.

There are a few areas of the live geological data stream on GeoNet that I hope will be improved. There is no data shown for earthquakes that occur in the South Pacific, which is of interest due to tsunami risks. New Zealand's own seismic sensor network is not large enough to locate these earthquakes accurately on its own, but GeoNet provides data to the United States Geological Survey (USGS) and the International Seismological Centre in the United Kingdom, so it should be possible to accumulate and display data for the entire planet on one website. In fact, the USGS already do so, although their map is missing a few of the minor ones in New Zealand).

Comments (0) | 20 May 2009