06/05/2014
Anyone with any knowledge of the history of the Vega Baja will be aware that the earthquake on 21st March 
1829 was a crucial event in the area, causing 389 deaths and necessitating the almost complete reconstruction of many of the towns in the south of the Costa Blanca.
That devastating earthquake measured an estimated 6.6 on the Richter scale, and if a minor tremor is actually felt by residents in the area the news is greeted with understandable trepidation. This was the case at 15.39 on Monday, when a minor tremor (1.4 on the Richter scale) was recorded 200 metres offshore from the Parque del Molino del Agua and the Playa de la Mata at a depth of 9 kilometres below the earth’s surface.
Due to the epicentre being so close to the surface the tremor was actually felt by residents in both Torrevieja and Guardamar del Segura, in spite of it being such a small tremor, and this latest seismic event comes less than a month after the last one: on 9th April a tremor measuring 1.7 on the Richter scale, centred just off the coast, was also felt by locals.
However, it must be emphasized that these really are MINOR tremors, caused by natural plate movements ( don´t forget, Spain and Africa were once joined).
To put things into perspective:
How does the Richter scale measure earthquakes?
The earthquake which flattened areas of Japan and caused massive damage was a 9 on the Richter scale.
The information below calculates the importance of a force 3.1 earthquake, a common occurrence along the faultline which skirts the Murcian, Almerian and Valencian coastline, using as an example one which took place not long ago off the Cabo de Palos coastline.
How is the Richter Scale calculated?
This quake in Cabo de Palos was a 3.
The quake in Japan was a 9.
So does this mean the Japan quake was 3 times bigger than our little Cabo de Palos quake?
No it doesn´t.
We asked a mathematician for their explanation, and they said it was very simple, ” The magnitude value is proportional to the logarithm of the amplitude of the strongest wave during an earthquake.”
Which is why you never ask a mathematician for a simple explanation about anything.
What this actually means in layman’s terms is that for every point moved up the scale, the ground motion is ten times greater. A recording of 7, for example, indicates a disturbance with ground motion 10 times as large as a recording of 6, and a recording of 8 indicates one ten times greater than a reading of 7.
Using this information, we can calculate that in fact, an earthquake measuring 9 on the Richter scale is one where the ground motion is no less than A MILLION TIMES GREATER than a reading of 3.
And in relation to the energy expended, every point moving up the Richter scale represent a multiplication by 30, so the energy released by the earthquake in Japan was 729 MILLION TIMES GREATER than in our little Cabo de Palos frisson.
So there you go, 3.1 on the Richter scale in Cabo de Palos
Not as newsworthy as it sounds after all.
Image: National Geographic Institute
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