Shaking the Gulf of Mexico

This morning, on 15072018 at 11:27hrs UTC (06:27 am CST), a small M3.7 earthquake rattled Puertro Rico.  A similar seismogram was recorded on both the E1TX Seismograph (shown in red) and Raspberry Shake (shown in blue). A 3.0 to 6.0 Hz bandwidth filter was applied to the Raspberry Shake seismogram.

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Comparison of seismograms from the 15July2018 11:27hrs UTC Puerto Rico earthquake.

 

TEACHING MOMENT: I See You Running

I see you running on the treadmill – when you began running, and when you completed your time goal.  Furthermore, I can show you the specific frequencies of the man-made seismogram.  On 13072018 and 09:46hrs UTC during the M6.4 Vanuatu Earthquake (specifically during the arrival of the Rayleigh and Love waves), the seismogram is partially convolved with a dominant “noise” factor as shown below.  The red circles denote frequencies from an actual seismic event, while the purple bracketed time shows the segment where a treadmill was running for 30 minutes.  The effect on the seismic event can be seen as several lines at frequencies which are multiples of ~5.0.

This is an excellent example of how we may interpret “noise”, particularly high noise-to-signal ratio time segments.  When viewing the Spectrogram View, instead of the Wave Amplitude View, the convolution is obvious.  For Station E1TX, we used a bandwidth filter to reduce the effect…. we chose a 3.0 to 6.4 Hz bandwidth filter as an attempt to increase the signal-to-noise ratio (meaning enhancing the signal and dampening the noise). The unfiltered seismograms are as images 1 and 2; the last image is the filtered seismogram.

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UNfiltered Wave Amplitude View Seismogram, Purple is bracketed noise; red is actual signal being detected.

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UNfiltered Spectrogram View Seismogram, Purple is bracketed noise; red is actual signal being detected.

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Raspberry Shake seismogram with 3.0 to 6.4 Hz bandwidth filter applied.

Lost in the Earth’s Shadow Zone – Large M6.4 Earthquake near Isangel, Vanuatu

Today, 13 July 2018, at 09:46hrs UTC (04:45am CST) a major earthquake with a magnitude M6.4 occurred near Isangel, Vanuatu.  Interestingly, Station E1TX is ~ 104 polar degrees away from the epicentral location – within the Earth’s seismic shadow zone and we were not expecting to detect and record very many wave forms.  As seen on the two seismograms below (red is from the EQ1, blue is the Raspberry Shake) only a few wave arrivals can be interpreted.  On the RS seismogram, the data recording is partially convolved with a nearby treadmill which was in use from ~5:25 to 5:55am CST.  Please see the next post which discusses recording short period, higher frequency “noise” and the use of filters.

The RS seismogram has a 3.0 to 6.4 Hz bandwidth filter applied.

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Raspberry Shake seismogram of the M6,4 Vanuatu earthquake.

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EQ1 seismogram of the M6,4 Vanuatu earthquake.

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Map of the epicenter of the M6,4 Vanuatu earthquake.

 

Small M4.4 Earthquake Off the Coast of Michoacan, Mexico

On 07/10/2018 at 07:50hrs UTC (02:50am CST), a small earthquake with magnitude 4.4 occurred offshore Mexico – near Michoacan.  Seismograms of the event are compared below, Station E1TX is ~17 pol deg away.

The Mexican West Coast has a high probability of experiencing moderate to large earthquakes.  Many vacationers do not recognize the seismic risk; TXESP strongly encourages all Mexican tourists and residents to maintain their knowledge of earthquake safety.

Japan Rattles Again, M5.9 Earthquake

At 11:23hrs UTC (6:23 am) a strong magnitude 5.9 #earthquake occurred offshore Japan – causing light shaking in the capital, Tokyo.  The event, with a focal depth of 40kms, is located 2500+km South of the July 6, 2018 M6.0 Yuhzno, Russia earthquake. Station E1TX is about 96 polar degrees away from the epicenter which is on the cusp of the “#seismic shadow zone” where seismic wave phases are limited / not detected due to the presence of Earth’s liquid outer core.  The P wave, or body wave, is highlighted by a yellow circle on the seismogram recorded by the Raspberry Shake #raspishake #Weston_Quakes

As noted before, earthquakes are not un-common for the region located near the Kuril Islands and #Kuril Trench.  Most importantly, no damaging ground shaking was detected near nuclear facilities.  Minimal personal damages were reported in the Chiba region.  No tsunami warning was issued.  Read more, HERE.

 

 

Comparison of the M6.0 in Russia

July 06, 2018, a large magnitude 6.0 earthquake occurred near Ozernovskiy, Russia at 01:40hrs UTC and had a focal depth of 79.8kms.  This region is known as “The Ring of Fire”; earthquakes are highly probable within this defined perimeter.  Shown is a comparison of two seismograms recorded at Station E1TX from TXESP’s EQ1 Seismograph and the Raspberry Shake Seismometer: the top image (in red) is a from an EQ1 Seismograph with a 10s filter, the image below (in blue) was recorded on the Raspberry Shake Seismograph with a bandwidth filter from 5.0 to 13 Hz.  Note that the EQ1 seismogram, set to record long-period waves, recorded the body waves while the RS seismogram, set to record shorter period events, is “missing” a few wave forms.  This event was approximately 76 pol deg away.  A map of the epicenter and the screenshot from the EQ1 are also shown.

06072018_0140_extract_RussiaCOMPARE06072018_0140_map_Russia06072018_0140_scrnsht_Russia

 

 

 

Sandy Valley, Nebraska

Today, July 05, 2018, a moderately-sized magnitude 4.5 earthquake occurred near Sandy Valley, Nebraska at 15:17hrs UTC (10:17am CST).  Earthquakes in the region of the Central United States are rare; however, a similar earthquake occurred 4 days earlier near Stapleton, NE.  Shown is an interpreted seismogram from TXESP’s Raspberry Shake Seismometer.

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Interpreted Sandy Valley, NE seismogram from TXESP’s Raspberry Shake.

05072018_1517_map_NE

Near Sandy Valley, NE

 

 

 

 

Hello Nebraska?

On July 02, 2018, a moderately-sized magnitude 4.1 earthquake occured near Stapleton, Nebraska at 08:42hrs UTC (03:42am CST).  Shaking is assumed to be light due to the small magnitude, and we assume no damages occur.  Earthquakes in the region of the Central United States are rare.

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Sweet Home Alabama, M2.9 Earthquake

On July 02, 2018, a small magnitude 2.9 earthquake shook the town of Muscle Shoals, Alabama, South of the University of North Alabama, at 19:29hrs UTC (02:29am CST).  Shaking was likely **not** felt due to the small magnitude, and we assume no damages occur.  NOTE:  Neither the EQ1, nor the Raspberry Shake, detected this very small earthquake.  The seismogram show where we would expect the P wave (the body wave) to have appeared if detected.

 

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