EARTHQUAKES - WHAT ARE THE LONG TERM TRENDS?
The outer shell of the earth is composed of a number of almost rigid "plates" that slowly move against each other. It is this geological feature that provides the conditions for major earthquakes to occur. Although they can occur anywhere on the planet with little warning, the most extreme earthquakes occur near the plate boundaries. Stresses can build up at these boundaries, caused by the general movement of the plates against each other over time, which is "bottled up" at the plate boundaries. It may then be released suddenly, in the form of an earthquake. Several boundaries are under deep water, but the effects spread for many miles, and so can be felt on land in these cases too. Tsunamis may be triggered bringing damage to coastal communities, in a wide area. Powerful earthquakes may also initiate volcanoes to erupt, in the vicinity or further afield, although this is not always the case, as it depends on the state of the magma chamber at the time.
A measurement of earthquake magnitude is the Richter scale. On a
logarithmic scale this measures the size and energy released from an earthquake. On this scale, there are usually dozens of "earthquakes" occurring daily, with a magnitude of below 2.5 . These are usually not felt by humans. It takes a much stronger earthquake for damage to occur. For example, a magnitude 6.0 earthquake is ten times larger than a magnitude 5.0, but it has 32 times the amount of energy released, so is more likely to cause damage.An earthquake registering between 6.0 and 6.9 could be considered fairly major. Above 7.0, the earthquake is considered more serious, with a larger area of damage anticipated. Loss of life is dependent on location (land/sea) as well as whether or not buildings can withstand the earth tremors. The larger the magnitude, the more likely fatalities will occur. The largest earthquake in recent history measured about 9.5 (Chile, 1960). It is not beyond possibility that a massive earthquake of magnitude 10.0 ( 10 )or 10.1 on the Richter scale could be produced on the planet, in extreme circumstances. This level of quake would cause damage to the earth's crust on a truly global scale, with the fault line likely to circle the entire planet, causing massive destruction on many continents and probably unbelievably high death tolls - although, by contrast, the energy produced by such an earthquake as this is only a tiny fraction of the energy the earth receives every day from the sun in the form of light and heat!
For the purposes of statistical recording below, only those earthquakes registering ABOVE 6.9 (ie a level of 7.0 or above) are now counted below. Major earthquakes, rather than the more regular and frequent lower intensity earthquakes, are judged to have a greater impact on geographic reach and damage, and are more likely to be recorded over a longer period of history.
It is interesting to note the following statistical records for earthquakes since 1863 across the planet. I have chosen a relatively long period each time, to allow true trends to be seen, and smooth out the effects of short term counts. (see below).
It is worth noting that our ability to record all earthquakes of 7.0 or above occurring across the planet prior to 1901 is uncertain, and so there is likely to be some incomplete data in the 19th century, because of this. It was only in 1897 that a global network of seismographs was deployed. The numbers shown for the period from 1863 to 1900 may therefore be lower than actual, although it is unlikely to be more than three or four times that shown. (records for major 'quakes were fairly good from the 1870s onwards). It is acknowledged that care and good judgement must be exercised in using global seismic data, as there can still be incomplete data from sources even after 1901. This report has been based on data available from USGS (NEIC) and other sources, in an attempt to cover as much of the available data as possible .
DATES FROM & TO PERIOD NO. EARTHQUAKES (Mag. > 6.99) --------------------------- ----------- ------------------------------ 1863 to 1900 incl 38 yrs 12 1901 to 1938 incl 38 yrs 53 1939 to 1976 incl 38 yrs 71 1977 to 2014 incl * 38 yrs 134 (to Nov. 2008) predict >180 in total. Reference list Jan 1977 to Jan 2007 only
* Although periods are shown up to 2014, this report was initially written in 2006. Therefore the final period (from 1977) will be updated as required until the end of 2014. In the meantime a predicted total is shown.
The earthquake (in Sea of Okhotsk, Russia) on 24th November 2008 is the last included in these numbers.
Apart from the "long-term" trends shown above, which show an ongoing persistent increase, it is perhaps more stark to record that earthquakes across the planet show a marked increase in activity since 1996. There has been very little change in the "detection rate" for these major earthquakes since, for example, 1977 - it is simply there are more major earthquakes occurring now, and this on an ever more frequent basis.
So, for example, between 1986 and 1996 (incl), a period of 11 years, there were "just" 15 earthquakes of magnitude 7.0 or greater. This is not markedly different (albeit a slight decrease) from previous (similar periods) of 20th century, where an average of about 18 might be expected
But between 1997 and 2007 (incl), a period of only 11 years, there were 99 earthquakes with magnitude 7.0 or greater : This is more than a six-fold increase on the previous decade - and is a stark increase on any earlier decades too.
The trends in nature here, particularly since 1997 support the wider realisation of prophesy about the "End Times", namely that an increase in earthquake activity is a pre-requisite for the "second coming of Jesus Christ" foretold in the bible. It does not indicate how close we are to this event, but suggests it is not too far away.
About the "End Times"
Speaking of the signs that will happen, leading to his return to judge the peoples of earth (at the end of the age), Jesus is quoted as saying ‘in various places there will be famines and earthquakes - these things are the beginning of birth pangs’ (ref: Matthew 24). Now, because birth pains begin small and then increase in intensity and frequency, this passage can be interpreted to mean that earthquakes (and famines) will increase both in frequency and impact/strength prior to Jesus’ second coming. Although Jesus is clear that no one will know the day or the hour, and his return will indeed happen “when you do not expect”, he does give us broad pointers, one of these being natural events – like earthquakes.
Future Trends
Past performance cannot necessarily be taken as a clear indication of future trends (unfortunately many scientists tend to assume too often that it is, by simply projecting forward on an existing trend, without considering other factors) so we must be careful how past events are interpreted. However, it is clear we are currently living in a time when earthquake frequency has increased, it will be interesting to see if the immediate future maintains this trend.
Other Notes
When there are multiple earthquakes (magnitude 7.0+) occuring within 5 days of each other in the same region, only one has been counted. This may result in slightly different (lower) numbers for earthquakes than might otherwise be listed, although consistancy in this approach makes historical comparisons more reliable, as large after-shocks were not always recorded (in addition to the "main" quake) in previous decades.
incl = inclusive dates.
References
Report produced by R Webb