COMPARING TECHNOLOGY: Recordings from an EQ1 and Raspberry Shake Seismographs (JUST RECORDED)

COMPARING TECHNOLOGY:  Recorded in the past hour, shown are two Indonesian earthquakes recorded on an EQ1 and Raspberry Shake seismographs. Both earthquakes had a magnitude M5.9 and occurred with 2 minutes of each other today, 02/02/2019, at 10:59 and 11:01hrs UTC and had depths of 10kms. The images compare two different seismographs – the #EQ1 and the #RaspberryShake.  On both seismograms we easily observe the first arrival (body) waves denoted by the yellow arrows.

A very fascinating wave phase, the PKP wave, was detected at our location in Spring, TX more than 148 polar degrees away.  This wave is unique because it is a wave which has propagated from the epicenter, through the mantle and outer core, and continued travelling back through the mantle towards Texas.  Can you see it? Can you see it on both seismograms?

Overall, a relatively good correlation between both the EQ1 and RS seismographs.  NOTE: the RS seismograph also detected the secondary (body) waves, the “S” waves.  This is not shown, due to scaling issues, on this slide.

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TEACHING MOMENT: From MEXICO to TEXAS to PENNSYLVANIA

GREAT TEACHING MOMENT: WAVE ATTENUATION – Shown is a comparison of the large magnitude M6.6 Mexican earthquake which occurred today, 02/01/2019, at 16:14hrs UTC and had a depth of 68kms. Notice the larger wave amplitudes at Station RAD87 (TX) VS. Station RA763 (PA).  Why does the Texas seismogram appear larger than the one recorded in Pennsylvania ?

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DYFI in Mexico This Hour?

Within the past hour, Mexican residents experienced a large magnitude M6.6 earthquake.  It occurred at 16:14 hrs UTC (or, 10:14 am CST) at a depth of 42 miles.  In the map shown below, the colored lines represent how much shaking could be felt during the earthquake.  The “hotter” colors experienced a great deal of shaking as expected – they are locations near the epicenter; “cooler” colors indicate that lighter shaking was felt but at much greater distances away from the earthquake.

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FOLLOW UP: Is it [a quake]? Or isn’t it?

In a previous post, TXESP discussed how Station E1TX recorded many ground motion events during a 24 hour time period.  Initial observations of the EQ1 Seismograph showed a couple of events with moderate amplitudes.  Analysis of the frequency spectra and additional graphs we may we have an educated interpretation to explain the recorded ground motion.

What We Know:  Nearby (within 1 miles), the Texas Department of Transportation has been making repairs to an overpass bridge on Interstate 45.

What We Observe on the Raspberry Shake Seismograph We can analyze three different views of an event using the #raspishake seismogram within the SWARM software.  For each event, we reviewed (a) the extracted seismogram, (b) a graph of the seismogram’s frequency spectra (frequency VS. power), and (c) a graph of the seismogram’s spectrogram (time VS. frequency).  In the slideshow, these two “unknown” events are compared with an analysis of an actual magnitude M3.4 earthquake in the US Virgin Islands on January 28, 2018 at 08:17hrs UTC.  Note the different characteristics (shapes) of the “unknown” events with the “known” earthquake.

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Lots of Quakes or Not a Shake?

Station E1TX has recorded many ground motion events during the last 24 hours, but are they [earth]quakes or simply ground shakes?  Looking at the display from the EQ1 seismograph, its easy to interpret a couple of events as moderate earthquakes – but they’re not.  Nearby (within 1 miles), the Texas Department of Transportation has been making repairs to an overpass bridge on Interstate 45.  It is highly likely that the majority of these recorded ground movements are related to the construction and retention of the adjacent Spring Creek.   Take a closer look at the events during the 0700, 1800 and 2100 hours -their shape appear very similar to real earthquakes, but closer inspection of the seismograms demonstrate that the wave character is not congruent with earthquakes.  Interestingly, the ground motions look very similar to each other – increasing seismic amplitudes with time – up until a point in time – followed by a dramatic drop in amplitude is common.  If these were body or surface waves, the seismic character would begin with strong amplitudes and diminish with time.  That is not the case today.  What construction activities do you think could have caused these ground motions?

 

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Columbia is Shaking Too

This morning, a magnitude M5.6 earthquake began shaking parts of Columbia.  The event happened on 01/26/2019 at 12:32hrs UTC (06:32 am CST).  It was 10km deep in the Earth and shaking was felt across 50% of the Country, including Bogata.  No damages have been reported by the Associated Press or local news outlets.

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7 Days, 54+ Earthquakes (M> 4.5) Around the “Rim of Fire”

)Do you track current events?  Did You Know that is the past 7 days, our Earth has experienced more than 54 moderate-to-strong earthquakes with magnitudes M>4.5 just around the Pacific Rim “Ring of Fire” ??! Three of these events (shown highlighted in teal-colored circles) had strong magnitudes: a M6.6 in Vanuatu (01/15/2019), a M6.7 in Chile (01/20/2019), and a M6.4 occurred today, (01/22/2019), in Indonesia.

Add less than two minutes into your routine….and watch the Earth MOVE, LIVE!  view USGS’ Global Maps HERE

** please note this post was published prior to the 01/22/2019 19:01hrs UTC Prince Edward Island earthquake with a magnitude of M6.72201019_usgs7days_map

 

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