There was a magnitude 5.0 earthquake in northwest Pennsylvania, right on the Ohio border.

Here is the seismic record from the College of Wooster.
Here is the seismic record from Univ. of Michigan (MichSeis).

Let's find out more about seismic history and risk in Ohio.

The US Geological Survey has a National Earthquake Information Center in Golden Colorado. Point your browser to http://www.geo.lsa.umich.edu/~ruff/980925.OhioPenn/usgs980925.jpg to see their record of the quake. (Now housed on the Univ. of Michigan server.).

1. When (in universal time) and where (lat., long., depth) did this quake take place?

2. The map at the site above shows topographic relief by color-coding. Green is close to sea level, pale green is a bit higher, yellow a bit higher in elevation, etc. Note the Appalachian Mountains on the map. Any plate boundaries would be shown by a thin yellow line.

For example: the Gulf of California:

Is there a lithospheric plate boundary in Ohio/Pennsylvania?

This is the largest earthquake in this area since a magnitude 5.0 which occurred January 31, 1986. There have been no reports of damage.

What is the seismic risk in Ohio? Let's look at a fact sheet from the Ohio Division of Geological Survey. Go to http://www.dnr.state.oh.us/odnr/geo_survey/geo_fact/geo_f03.htm.

3. What is the record of earthquakes in the Anna area, Shelby county, Ohio?

4. What are the suggested causes for Ohio earthquakes?

5. Why is it hard to assess seismic risk in this part of the world?

6. Ohio is on the edge of the New Madrid seismic zone. Go to http://www.eas.slu.edu/Earthquake_Center/SEISMICITY/NewMadridGeneral.html. What happened in New Madrid Missouri in the early 1800's?

Well, but what has been the record of earthquakes in the last 25 years or so? A map of instrumentally recorded earthquake epicenters from 1975 through 1995 is at St. Louis University: http://www.eas.slu.edu/Earthquake_Center/SEISMICITY/newmadrid1975-1995.html. Note: most of these earthquakes are small and not felt.

9. Do you see a pattern of sorts? Where & how are the earthquakes clustered?

A list of recent ( i.e. this year) earthquakes from CERI is at http://www.eas.slu.edu/Earthquake_Center/NEW/localmaps.html.
Scroll down to see the more recent ones.

Also, look at this map (http://folkworm.ceri.memphis.edu/recenteqs/) of recent earthquakes in the Central US. Have any earthquakes happened in the last 6 hours? The last week?

10. When and where was the most recent earthquake listed by CERI? Most of the recorded earthquakes have what range of magnitudes: 1 to 3, 3 to 5, 5 to 7?

So. A magnitude 5.0 earthquake in Ohio is somewhat unusual. What is the magnitude of small, moderate and large earthquakes in the rest of the world? Let's see.

Point your browser to
http://wwwneic.cr.usgs.gov/neis/weekly/weekly_locations.htm. (The National Earthquake Information Center again) This site has a map that shows the epicenters of about 3 week's worth of earthquakes in the world - and only the larger ones.

If the link doesn't work: Look at this map, as of Sunday afternoon:

11. Where do most earthquakes happen?

12. Note the color code for depth of an earthquake. Where do the deep earthquakes seemed to concentrated? What is the plate tectonic setting for these deep earthquakes?

13. Why isn't the USGS expecting any earthquakes with a focus depth of greater than 800 km?

The USGS also maintains a web page that is a Near-Real Time Earthquake Bulletin: http://wwwneic.cr.usgs.gov/neis/bulletin/bulletin.html.

If this link doesn't work, click here. 14a. At the time you are visiting this page, which is:

14b. where is the most recent earthquake? How big was it?

15. Note that this page only lists the last 21 big earthquakes worldwide. About how many big earthquakes happen per day? You can estimate this from this page - how many days are included here?

16. Does the number of earthquakes surprise you? Would you agree that the earth is an active planet?

Last updated: Sept. 21, 2000.

koziol@notes.udayton.edu

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The graphics on this page are courtesy of Jelane's free web graphics