SG Broadband Community

Q: Why are we having so many earthquakes? Has earthquake activity been increasing? Does this mean a big one is going to hit? OR We haven't had any earthquakes in a long time; does this mean that the pressure is building up?

A: Although it may seem that we are having more earthquakes, earthquakes of magnitude 7.0 or greater have remained fairly constant throughout this century and, according to our records, have actually seemed to decrease in recent years.

There are several reasons for the perception that the number of earthquakes, in general, and particularly destructive earthquakes is increasing.

1) A partial explanation may lie in the fact that in the last twenty years, we have definitely had an increase in the number of earthquakes we have been able to locate each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications.

In 1931, there were about 350 stations operating in the world; today, there are more that 4,000 stations and the data now comes in rapidly from these stations by telex, computer and satellite. This increase in the number of stations and the more timely receipt of data has allowed us and other seismological centers to locate many small earthquakes which were undetected in earlier years, and we are able to locate earthquakes more rapidly.

The NEIC now locates about 12,000 to 14,000 earthquakes each year or approximately 50 per day. Also, because of the improvements in communications and the increased interest in natural disasters, the public now learns about more earthquakes. According to long-term records (since about 1900), we expect about 18 major earthquakes (7.0 - 7.9) and one great earthquake (8.0 or above) in any given year. However, let's take a look at what has happened in the past 32 years, from 1969 through 2001, so far. Our records show that 1992, and 1995-1997 were the only years that we have reached or exceeded the long-term average number of major earthquakes since 1971. In 1970 and in 1971 we had 20 and 19 major earthquakes, respectively, but in other years the total was in many cases well below the 18 per year which we may expect based on the long-term average.

2) The population at risk is increasing. While the number of large earthquakes is fairly constant, population density in earthquake-prone areas is constantly increasing. In some countries, the new construction that comes with population growth has better earthquake resistance; but in many it does not. So we are now seeing increasing casualties from the same sized earthquakes.

3) Better global communication. Just a few decades ago, if several hundred people were killed by an earthquake in Indonesia or eastern China, for example, the media in the rest of the world would not know about it until several days, to weeks, later, long after such an event would be deemed “newsworthy”. So by the time this information was available, it would probably be relegated to the back pages of the newspaper, if at all. And the public Internet didn't even exist. We are now getting this information almost immediately.

4) Earthquake clustering and human psychology. While the average number of large earthquakes per year is fairly constant, earthquakes occur in clusters. This is predicted by various statistical models, and does not imply that earthquakes that are distant in location, but close in time, are causally related. But when such clusters occur, especially when they are widely reported in the media, they are noticed. However, during the equally anomalous periods during which no destructive earthquakes occur, no one deems this as remarkable.

A temporal increase in earthquake activity does not mean that a large earthquake is about to happen. Similarly, quiescence, or the lack of seismicity, does not mean a large earthquake is going to happen. A temporary increase or decrease in the seismicity rate is usually just part of the natural variation in the seismicity. There is no way for us to know whether or not this time it will lead to a larger earthquake. Swarms of small events, especially in geothermal areas, are common, and moderate-large magnitude earthquakes will typically have an aftershock sequence that follows. All that is normal and expected earthquake activity.

9mmprincess wrote:I dont believe in the 2012 nonsense, but in the last couple weeks there have been a lot of earthquakes. I believe the above article was written more generally, for the last few years, no? In the last two/two and a half weeks we've had like six or seven good sized earthquakes. I cant help thinking somethings up.

JBrazen wrote:Another quake today...5.8 in the Cayman Islands.

MissTynker2 wrote:Haiti hit again! To me that is no aftershock...that's a brand new quake!

http://latimesblogs.latimes.com/laplaza ... sleep.html

jeremyboycool wrote:"A temporal increase in earthquake activity does not mean that a large earthquake is about to happen. Similarly, quiescence, or the lack of seismicity, does not mean a large earthquake is going to happen. A temporary increase or decrease in the seismicity rate is usually just part of the natural variation in the seismicity. There is no way for us to know whether or not this time it will lead to a larger earthquake. Swarms of small events, especially in geothermal areas, are common, and moderate-large magnitude earthquakes will typically have an aftershock sequence that follows. All that is normal and expected earthquake activity. " - From the article.

A small pre-dawn earthquake has hit northern Illinois, startling sleepy-eyed residents as far away as Iowa and Indiana, but no damage or injuries were immediately reported.

The U.S. Geological Survey says the 3.8-magnitude earthquake hit about 50 miles northwest of Chicago at 4 a.m. Wednesday. The USGS initially reported the magnitude as 4.3 but later downgraded it.

USGS geophysicist Amy Vaughan says such quakes are rare in northern Illinois.

YARDofSTUF wrote:OMG everyone panic!

Oh wait nm, its just Sava.

Just cause its rare for the area doesn't mean we're getting more.

As for there being more in general recently, reread what Jeremy posted.

Sava700 wrote:I think its safe to assume there are more than usual according to reports coming out...

YARDofSTUF wrote:You mean like the report Jeremy posted saying there aren't more than usual?

Sava700 wrote:There are people that write articles against it and people that write articles for it... You have some scientists that say global warming is happening and some that say it's not.

Sava700 wrote:There are people that write articles against it and people that write articles for it... You have some scientists that say global warming is happening and some that say it's not.

YARDofSTUF wrote:So where are these artlices about the earthquake numbers increasing and leading to a big event?

Sava700 wrote:You know how to use Google as much as I do.... look em up for yourself. I just posted a news article about another one, not in the mood to argue statistics with you.

jeremyboycool wrote:I got that article from the same web site you posted in the OP.

9mmprincess wrote:argue argue argue fight fight fight

YARDofSTUF wrote:No rabble?

Debbie wrote:http://earthquake.usgs.gov/earthquakes/ ... s_all.html

Interesting site. Although, I would assume the repeat events are just aftershocks.

9mmprincess wrote:rabble rabble rabble!

Dan wrote:at least here,there are and always have and will in the future continue to have sometimes hundreds of earthquakes daily,that's normal

http://quake.usgs.gov/recenteqs/latest.htm

http://earthquake.usgs.gov/

YARDofSTUF wrote:OMG everyone panic!

Oh wait nm, its just Sava.

Just cause its rare for the area doesn't mean we're getting more.

As for there being more in general recently, reread what Jeremy posted.

JawZ wrote:http://www.sciencedaily.com/releases/20 ... 140817.htm

It is possible that increased seismic activity could be localized. Just because quake activity is even doesn't represent their actual seismic potential. In this case, frequency doesn't equal potential energy released. The question to ask is, are quakes getting stronger (magnitude) or might they be leading to much more significant quake activity?

JawZ wrote:7.0 just hit off Okinawa...3ft Tsunami warning.

A 7.0-magnitude earthquake struck Japan's Ryukyu Islands early Saturday, the U.S. Geological Survey reported.

Soon after the 5:31 a.m. (3:31 p.m. Friday ET) quake, Japan's Meteorological Agency issued a tsunami advisory, recommending that people on the Okinawa Islands evacuate from the seashore. The advisory also affected the Amami Islands and Tokara Islands.

The agency said the expected tsunami height was about 0.5 meters, or 20 inches.

The quake was centered about 6 miles (10 km) deep, about 53 miles (85 km) from Okinawa.

A massive iceberg struck Antarctica, dislodging another giant block of ice from a glacier, Australian and French scientists said Friday.

The two icebergs are drifting together about 62 to 93 miles (100 to 150 kilometers) off eastern Antarctica following the collision on Feb. 12 or 13, said Australian Antarctic Division glaciologist Neal Young.

The dislodging occurred because of the iceberg's latest location and water that had warmed during Antarctica's summer, leaving less sea ice, Legresy said.

Some experts are concerned about the effect of the massive displacement of ice on the ice-free water next to the glacier, which is important for ocean currents, while others are less concerned.

A massive magnitude 8.8 earthquake rocked Chile early Saturday, killing at least 78 people and triggering tsunami warnings for the entire Pacific basin.

"This is a major event. This happened near some very populated areas," said Randy Baldwin, a geophysicist with USGS. "With an 8.8 you expect damage to the population in the area."

"Sea level readings indicate a tsunami was generated. It may have been destructive along coasts near the earthquake epicenter and could also be a threat to more distant coasts," the warning center said. It did not expect a tsunami along the west of the U.S. or Canada but was continuing to monitor the situation.