The VERY STRONG, WINDY Polar Vortex made it through to Houston last night. Interestingly, you can see the affect of the high winds and gusts (BLUE arrow) on the EQ-1 seismograph. The “weather noise” has a large amplitude, and it has masked the signal of the first arrival OR (2) the quake was too deep at 620kms deep in Brazil at 13:30hrs UTC. The red underlined section is where we expect the first arrival, or the P wave, for the Brazilian earthquake.
A moderate earthquake occurred offshore MX yesterday (blue arrow) – this station is calling it the “mystery earthquake” because we cannot see any of the body waves appear; the epicenter was “close” to station E1TX – about 15 polar degrees away and at a depth of 85km. Unfortunately the P wave was not detected. – it’s likely that (1) the amplitude/noise ratio was too small OR (2) the first arrival occurred during the downtime of the seismogram between 16:35 to about 16:42 hrs UTC. The very large earthquake earlier in the image is the M7.9 Papua New Guinea earthquake.
This morning at 10:51hrs and at 11:27hrs UTC two HUGE earthquakes occurred in Papua New Guinea. The main shock had a Mw magnitude 7.9 and the 30-minute delayed aftershock was a Mw magnitude 6.3. The earthquakes focus points were about 100km depth. Because the aftershock followed so quickly, E1TX is unable to de-convolve the two events and yield two different seismograms; therefore, only the first arrival of the main shock is presented.
Earthquake waves travel through the Earth in a spherical dispersion (and get refracted and reflected at geological boundaries) – earthquake waves do not travel in straight line. This is due to the shape of the Earth which is mostly spherical. For circles, Scientists measure the distance between two points using polar coordinates to measure that distance. For example, an earthquake in Guatemala occurred today 12/12/2016, and it was recorded here in Spring, Texas. In order to measure the distance between the two locations, we use an algorithm by the University of Wisconsin – River Falls. Find out the latitude, longitude, and height (in kms) of your site, and then check the ‘USGS Latest Earthquakes Site’ to find the similar coordinates of the earthquake event. The link is highlighted above so that you can try!
During an online discussion with Seeley Lake, MT students, a magnitude 6.9 aftershock occurred in the Solomon Islands. The high amplitude “spikes” are “human-made earthquakes” we made as part of a demonstration. The earthquake’s long period waves are highlighted in yellow.
Seeley Lake, MT students had a dynamic online discussion with Texas Educational Seismic Project on 12/09/2016. We discussed how the EQ-1 seismograph works to detect and record global earthquakes – the high amplitude “spikes” are “human-made earthquakes” we made as part of a demonstration. The black arrow on the seismogram points to an aftershock event which occurred during the demonstration in the Solomon Islands.