Magnitude 5.5 – ONTARIO-QUEBEC BORDER REGION, CANADA

A magnitude 5.5 earthquake occurred this afternoon on the Ontario-Quebec border at 7:41:41 UTC or 1:41:41 PM local time.  This earthquake was felt in Millersburg, OH.  My brother called me to ask if we had just had an earthquake as they had felt it in their office.  It was on my seismograph but we had to wait several minutes to get the report from the USGS.  The peaks were not straight forward to pick accurately but it was clear that it was some distance off when I looked at it.

The arrival time information from the USGS Arrival Time Calculator is shown below for our location:

  DATE-(UTC)-TIME    LAT    LON     DEPTH MAG   Q   COMMENTS
  2010/06/23 17:41:41  45.87N  75.46W  15.7 5.5      us: ONTARIO-QUEBEC BORD REG.
   Expected 1s period body wave amplitude     [  4.12E-02 µm]  [  2.59E-01 µm/s]

 delta   azimuth (degrees clockwise from north)
 (deg)      eq-to-station     station-to-eq
  7.08          223.8              39.4

                 travel   arrival time
    #  code      time(s)  dy hr mn sec
    1  Pn         102.98   0 17 43 23
    2  Pb         122.60   0 17 43 43
    3  Sn         184.17   0 17 44 45
    4  Sb         212.45   0 17 45 13
    5  PKiKP      992.45   0 17 58 13

Postscript:

The USGS reduced the magnitude estimate to 5.0.
 

Magnitude 5.7 – SOUTHERN CALIFORNIA

A Magnitude 5.7 earthquake in Southern California as recorded in northeastern Ohio.

Magnitude 7.5 – NICOBAR ISLANDS, INDIA REGION

A strong 7.5 Magnitude earthquake in the Nicobar Islands this afternoon as recorded in northeastern Ohio.

Magnitude 6.3 & 6.0 – BERING SEA

Magnitude 6.3 - BERING SEA

Magnitude 6.3 earthquake in the Bering Sea last evening.  A second, Magnitude 6.0 tremor occurred about 5 minutes later in the same location.  The travel time curves are placed based on the first, larger one.  The unmarked arrival to the right of the SS curve is the SS arrival for the Magnitude 6.0 event as shown below.  In this image the travel time curves are placed based on the second Magnitude 6.0 event.  Overlapping returns are usually more difficult to extract from a single trace than these signals.

As an aside, I have Amaseis running on an old HP/Compaq notebook computer with Windows XP Pro.  Even though Windows provides a mechanism for updating the system clock using some variant of internet time, it doesn’t allow the user to set the frequency of the update.  The clock was running about 2 minutes fast when these earthquakes took place so I have to compensate for the actual time difference in the analysis.  I need to find a better way to update the system clock.   Postscript:  I had used a program called NMEATime in conjunction with a GPS receiver to set the time on my previous logging computer.  I couldn’t use it with the GPS on the notebook because it only has one serial port.  However, the program can also synchronize to network time servers at a user programmable interval so I installed it to synchronize the system clock.

Magnitude 6.0 - BERING SEA

Magnitude 6.9 – BAJA CALIFORNIA, MEXICO

A strong Magnitude 6.9 earthquake occurred at the northern end of the Gulf of California this evening at 22:40:39 UTC.  The surface wave signal went offscale for roughly 15 minutes on my seismograph in northeastern Ohio.

The travel time information is shown below:

  DATE-(UTC)-TIME    LAT    LON     DEPTH MAG   Q   COMMENTS
  2010/04/04 22:40:39  32.09N 115.25W  32.3 6.9      CI: BAJA CALIFORNIA, MEXICO
   Expected 20s period surface wave amplitude [  3.14E+02 µm]  [  9.88E+01 µm/s]
   Expected 1s period body wave amplitude     [  2.69E+00 µm]  [  1.69E+01 µm/s]

 delta   azimuth (degrees clockwise from north)
 (deg)      eq-to-station     station-to-eq
 28.05           63.0             263.1

                 travel   arrival time
    #  code      time(s)  dy hr mn sec
    1  P          348.27   0 22 46 27
    2  pP         357.60   0 22 46 36
    3  sP         361.79   0 22 46 40
    4  pP         362.32   0 22 46 41
    5  sP         366.59   0 22 46 45
    6  PnPn       396.29   0 22 47 15
    7  PP         411.89   0 22 47 30
    8  PcP        542.03   0 22 49 41
    9  S          631.62   0 22 51 10
   10  pS         642.31   0 22 51 21
   11  sS         647.64   0 22 51 26
   12  SPg        649.31   0 22 51 28
   13  SnSn       709.29   0 22 52 28
   14  ScP        760.33   0 22 53 19
   15  PcS        764.25   0 22 53 23
   16  ScS        992.93   0 22 57 11
   17  PKiKP      997.98   0 22 57 16
   18  pPKiKP    1008.66   0 22 57 27
   19  sPKiKP    1012.55   0 22 57 31
   20  SKiKP     1206.72   0 23  0 45
   21  PKKPdf    1903.14   0 23 12 22
   22  SKKPdf    2111.88   0 23 15 50
   23  PKKSdf    2115.77   0 23 15 54
   24  SKKSdf    2324.45   0 23 19 23
   25  P'P'df    2411.51   0 23 20 50
   26  P'P'ab    2527.79   0 23 22 46
   27  S'S'df    3258.93   0 23 34 57
   28  LQ         711.89   0 22 52 30
   29  LR         790.10   0 22 53 49

Postscript:

USGS subsequently re-estimated the magnitude to be 7.2 and raised the hypocenter estimate from ~32 km to 10 km.

Large Earthquake in Ohio?

With the recent earthquakes in Haiti and Chile I have been thinking about the earthquake potential here in Ohio. Unlike Haiti and Chile, Ohio is not on the edge of a tectonic plate. But we still have an earthquake now and then. Several years ago, I found a USGS website with the capability to plot the location of historical earthquakes in a given geographical area. I created a map, shown above, for earthquakes in the eastern United States.  The map below shows additional earthquakes in southeastern Canada.

Human beings have an innate capacity for seeing patterns, sometimes even where there are none. Being human, I can’t escape that tendency. When I look at my map, I see two broad lines of earthquakes, one on each side of the Appalachian mountains and running roughly parallel to the eastern coast of the country. I speculate that these earthquakes occur on cracks and faults in the earth’s crust that are remnants of the collisions and breakups of supercontinents hundreds of millions of years ago. While most of the earthquakes on the map are minor, a number of them have caused structural damage, most notably to chimneys and other masonry structures. A few have been large. The 1811-1812 series of earthquakes in the region around New Madrid, Missouri are among the largest known earthquakes the conterminous United States. That includes California! While they occurred prior to the invention of the seismograph the magnitudes of two of those earthquakes are estimated to have been between 7.2 and 8.0. These and several other large historical earthquakes in the eastern United States and Canada are listed below.

The New Madrid series, including:

1811, December 16, 08:15 UTC. Northeast Arkansas  Magnitude ~7.2 – 8.1

1811, December 16, 14:15 UTC, Northeast Arkansas

1812, January 23, 15:00 UTC, New Madrid, Missouri  Magnitude ~7.0 – 7.8

1812, February 7, 09:45 UTC, New Madrid, Missouri  Magnitude ~7.4 – 8.0

M7.3 Charleston, SC, 1886

Large earthquakes in southeastern Canada, including:

The 1925 Charlevoix-Kamouraska earthquake (Magnitude 6.2);

The 1929 Grand Banks (or Laurentian Slope) earthquake (Magnitude 7.2) which generated a 7 meter tsunami in Newfoundland;

The 1935 Timiskaming (or Témiscaming) earthquake (Magnitude 6.2);

The 1944 Cornwall-Massena earthquake (Magnitude 5.6).

The 1988 Saguenay earthquake (Magnitude 5.9).

There are a number of named seismic zones along the western line of earthquakes. The most famous is the New Madrid seismic zone but the Charlevoix-Kamouraska zone in Quebec also generates a lot of earthquake activity.  In fact all of the Canadian earthquakes listed above except for the Grand Banks event lie on the “line” of earthquakes that runs through Ohio.  Between those two zones there are other lesser known zones in southern Illinois/Indiana, western Ohio near Anna, and northeastern Ohio near Painsville. But the activity seems to thin out through Ohio…is that because that region is just more stable or is it because the stresses are still accumulating in the faults here?  There have been large historical earthquakes on both ends of “our line”.   Ohio is in the middle.  Could we have a large earthquake here in Ohio?

My amateur speculations are generally corroborated in the two page GeoFacts No.3 published by the Ohio Department of Natural Resources Division of Geological Survey. But my questions are not answered…the nature of Ohio’s subterranean faults is just not known.

Earthquakes are not something we live with on a daily basis in Ohio.  Most people in Ohio don’t even think about earthquakes.  I don’t expect a large earthquake here during my lifetime…but knowing what I know, however limited that knowledge is,  I won’t be surprised if there is one.

Postscript:

A little more web browsing yielded a more complete description of Ohio seismicity and a listing of significant earthquakes in Ohio…. Earthquakes in Ohio by Michael C. Hansen.  Interesting reading.

Magnitude 8.8 – OFFSHORE MAULE, CHILE

A Great Earthquake of Magnitude 8.8 occurred off the coast of Chile this morning at 06:34:14 UTC.  The extracted signal from my seismograph in northeastern Ohio shows severe clipping on the surface wave portion of the signal due to the size of this earthquake.  This earthquake was approximately 500 times stronger (energy released)  than the earthquake in Haiti last month.

The earthquake occurred offshore along the convergence zone of the Nazca and South American plates.  This is a thrust fault due to the subduction of the Nazca plate under the South American plate.  The earthquake occurred just 250 km north of the location of the largest earthquake recorded on instruments, a magnitude 9.5 event in May of 1960.   A series of significant aftershocks is expected.  One of these, at magnitude 6.9, occurred at 08:01:24 UTC.

The type of fault and its location and magnitude prompted several tsunami warnings and watches.  The following tsunami levels have been reported:

 Location                   Lat.   Lon.    Time        Amplitude
 ------------------------  -----  ------  -------     -----------

 40min     SAN FELX    C  26.3S   80.1W  0809UTC       0.69M/2.3FT
 27min     Corral  Chile   39.9S   73.4W  0727UTC      1.45M/4.8FT
 40min     Talcahuano  C   36.7S   73.1W  0659UTC      1.80M/6.0FT
           VALPARAISO  C   33.0S   71.6W  0708UTC      2.60M/8.6FT

Time - Time of measurement.
Amp. - Tsunami amplitudes are measured relative to normal sea  level.  It is NOT crest-to-trough wave
height.  Values are given in both meters (M) and feet (FT).

The phase arrival time information for my location is shown below:

 delta   azimuth (degrees clockwise from north)
 (deg)      eq-to-station     station-to-eq
 76.50          352.8             172.4

                 travel   arrival time
    #  code      time(s)  dy hr mn sec
    1  P          706.39   0  6 46  0
    2  pP         717.33   0  6 46 11
    3  PcP        717.67   0  6 46 11
    4  sP         721.65   0  6 46 15
    5  PP         878.25   0  6 48 52
    6  PKiKP     1050.19   0  6 51 44
    7  pPKiKP    1061.66   0  6 51 55
    8  sPKiKP    1065.86   0  6 51 59
    9  SKiKP     1261.00   0  6 55 14
   10  S         1290.15   0  6 55 44
   11  pS        1304.08   0  6 55 58
   12  sS        1308.82   0  6 56  2
   13  SKSac     1314.20   0  6 56  8
   14  SKKSac    1315.27   0  6 56  9
   15  ScS       1319.14   0  6 56 13
   16  SPn       1326.49   0  6 56 20
   17  pSKSac    1329.16   0  6 56 23
   18  PnS       1331.50   0  6 56 25
   19  sSKSac    1333.57   0  6 56 27
   20  SS        1586.24   0  7  0 40
   21  PKKPdf    1846.31   0  7  5  0
   22  PKKPbc    1858.17   0  7  5 12
   23  SKKPdf    2057.33   0  7  8 31
   24  PKKSdf    2061.53   0  7  8 35
   25  SKKSdf    2272.32   0  7 12  6
   26  P'P'df    2341.82   0  7 13 15
   27  S'S'df    3201.00   0  7 27 35
   28  S'S'ac    3212.35   0  7 27 46
   29  LQ        1941.66   0  7  6 35
   30  LR        2154.97   0  7 10  8

Magnitude 7.0 – HAITI REGION

Raw seismogram of Magnitude 7.0 earthquake in Haiti as detected in northeast Ohio late this afternoon.

Moving Up in the World

A couple of weeks ago, in a telephone conversation, my older son mentioned that it would be interesting to see if we could measure the Doppler shift in a satellite radio beacon as it passed overhead. He suggested, if I was interested, that he could bring along a radio and we could try it when they came home to visit at Christmas. Of course I was interested!

After supper on Christmas evening, he found a candidate satellite and set up the radio. We fed the audio from the radio to the line input of my MacBook to make the recording and do the analysis. The long and the short of it was that we picked off a nice Doppler shift on two passes, one on the evening of the 25th and one on the evening of the 26th. The Raven Lite software was great for monitoring the signal, both visually and audibly but it had the shortcoming of limiting the recording time to only a minute. For the pass on the 26th, we split the signal and used his MacBook to record the full pass of several minutes into one file using Audacity while keeping Raven Lite running on mine. Since the frequency shift was greater than the radio’s passband, it had to be retuned a few times.

I picked several points off of each file and manually adjusted each point for the time and any retuning of the receiver as needed. Then I used my linear path model for the curve fit after replacing the speed of sound with the speed of light. The first pass data fit very nicely. I haven’t done the fit on the second pass yet. Once I do a little more analysis, I’ll put up a page on it.

My son reminded me that there was a docudrama on PBS’s Nova many years ago (December 1989) called “The School Boys Who Cracked the Soviet Secret” about a science class in a private boys school in England that did a similar analysis on the Sputnik satellite right after it was launched. It would be interesting to watch that again.

This is a very interesting subject that has lots of avenues to study in more detail. We’ll have to see what develops as time passes. For right now though, the basic process was pretty easy, gives me a lot of things to think about… and was very cool.

NetQuakes

The American Geophysical Union held their Fall Meeting in San Francisco this week. My wife heard a report on some of the happenings of interest to the general public on the radio this afternoon. One of the reports described the NetQuakes program being undertaken by the U.S. Geological Survey.

The NetQuakes program asks volunteers to host small seismographs at their homes in order to increase the number of seismographs in the San Francisco Bay area.  These appear to be strong motion sensors based on triaxial accelerometers and record data only when triggered by an acceleration of 0.25% g.  The triggered waveforms are sent to the USGS via wifi through the vounteer’s internet connection and are immediately analyzed for possible earthquake events.  The triggered waveforms are also displayed on a page off of the NetQuakes homepage. 

As I was exploring the NetQuakes site, I noticed that several, but not all the stations showed a coherent signal at about 10:16:30 on Dec 18, 2009.  I clicked on on one, J021-NC.  Then I went the USGS Earthquake Hazards page to look for small California earthquakes at that time.  I looked first at the listing for Magnitude 3+ events but didn’t find any at the proper time, which I should have expected from the limited number of stations reporting the event.  When I looked at the Magnitude 1+ list I found a Magnitude 1.8 earthquake just a few miles from the J021-NC station.  The station names can be determined by clicking on the location map at the location indicators…pretty cool and it should give them very fast earthquake severity and location information.