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On 4 September 2010 there was a Magnitude 7.1 earthquake in Mid Canterbury New Zealand, which caused extensive damage in Christchurch and revealed a hidden fault line under the Canterbury Plains. Earthquakes are relatively common in New Zealand, there are approximately 15,000 per year with about 250 being strong enough to be felt, hence the country’s nickname the Shaky Isles. In Australia there are approximately 200 earthquakes per year, however most are too weak to be felt. Why is there such a difference in earthquake activity between the two countries?

The crust of the Earth is divided into a patchwork of tectonic plates which are rigid but float on the hotter, viscous layer of the Earth’s mantle, these plates move continuously and independently.  There are 7-8 major plates and many minor ones. The movement of the plates causes friction which builds up stress in the brittle upper layers of the plates, at a certain threshold the rocks break and energy is released causing an earthquake.

An earthquake originates at a point called the epicentre and produces three types of seismic waves, which radiate from this point. The fastest are P waves, compression waves that travel 14,000 – 28,000 kms/hour. Then there are S waves which travel at 9,000 – 14,000 km/hour, these move at right angles to the direction travelled, they cannot travel through liquids and usually cause the most damage. The slowest are surface waves, which can travel around the whole earth until they are too small to measure.
Seismic waves that originate from the largest earthquakes can travel inside the Earth for up to a month, the vibrations create a sound but its tone is so low (1 cycle per hour) that it can only be heard by special instruments.

In order to measure earthquakes two different scales have been developed:

The Richter scale was invented by Californian seismologist Charles Richter; it measures the magnitude of energy released at the epicentre on a mathematical scale. It is calculated by comparing wavelengths of seismic waves 100 kms from the point above the epicentre. Less than 2.0 is a micro quake that could not be felt, 8.6 would be the equivalent of 10,000 atomic bombs, 10+ has never been recorded.

The Mercalli Intensity Scale is a more subjective, descriptive scale that measures the effect on the natural and human environment. MM1 is an imperceptible earthquake with no measurable effect, MM12 causes complete devastation.

The reason that New Zealand has so many earthquakes is because it located over the boundary of the Australian and Pacific tectonic plates, the movement of the plates generate earthquakes. Australia is at low seismic risk because the Australian continent is located at the centre of the Australian tectonic plate and there are no large active fault lines. However no place on Earth is immune to earthquakes and even in the centre of a tectonic plates the stress on the plate boundaries can cause intra plate earthquakes.

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Why does attentiveness to nature matter? In a very fundamental sense, we are what we pay attention to. Paying heed to beauty, grace, and everyday miracles promotes a sense of possibility and coherence that runs deeper and truer than the often illusory commercial, social "realities" advanced by mainstream contemporary culture. ... Our attention is precious, and what we choose to focus it on has enormous consequences. What we choose to look at, and to listen to--these choices change the world. As Thich Nhat Hanh has pointed out, we become the bad television programs that we watch. A society that expends its energies tracking the latest doings of the celebrity couple is fundamentally distinct from one that watches for the first arriving spring migrant birds, or takes a weekend to check out insects in a mountain stream, or looks inside flowers to admire the marvelous ingenuities involved in pollination. The former tends to drag culture down to its lowest commonalities; the latter can lift us up in a sense of unity with all life. The Way of Natural History, edited by Thomas Lowe Fleischner and published by Trinity University Press (Texas)