Comparing siesmic tremor with surface events

Three events late May 2018 were added to the graph of seismic data. Time for this graph was adjusted so data points represent the end of a 6 hour average instead of the start of a six hour period.


The best time stamp for the opening of Fissure 24 I was able to find was 10 am the morning of May 27, 2018. Fissure 24 produced a very large flow and this may account for the dip in seismic tremor level.


Fissure 8 reopened the afternoon of May 28th, 2018.  This photograph of fissure 8th taken on May 28th by Robert Finlay and posted to his FaceBook account Hawaii Tracker shows just how big that reopening was. Likely this accounts for the very marked drop off in seismic level at seen by ERZ1 and ERZ2. Again PHOD may be too close to the action and experiencing the pounding as lava falls back to the earth, so background noise on PHOD is likely abnormally high.

On May 28th 2018 after looking at the low point for ERZ1 & 2 I went out on a limb and predicted that seismic levels would rise back up again and something would give way around 1-2 AM the night of May 29th, 2018. Specifically I was predicting a new fissure to open and I said it was far more likely to occur uprift. Seismic levels did in fact rise again. They peaked right around the time I mentioned too. However, there was no new fissure opening.

Instead, there was an earthquake right at 1:56 am HST. It was a very localized earthquake that showed up very well on the seismograph for both ERZ1 & 2.

ERZ1 showing localized earthquake at 1:56 am May 29th, 2018

Just after the earthquake, seismic tremor level at both ERZ1 & 2 dropped. However, they didn't drop for long. ERZ2 levels, the red line, rose more sharply and to a higher level than ERZ1. My conclusion is, and again I am not an expert and this is speculation, the probability of a downrift fissure opening is not as low as I thought yesterday. In fact, I think it is higher and more likely to occur closer to ERZ2 than ERZ1. The sudden drop in tremor level at ERZ1 & 2 could be due to that earthquake and the opening of a channel for lava to intrude into the area. The rise could be interpreted as meaning that the newly available room for lava quickly filled and now tensions are building again. Those tensions could very well mean an outbreak down rift from current activity.

Again I am not an expert.

One seismic event of note, that was not due to seismic tremor, was at 5:39 PM HST. That event was a 4.1 magnitude earthquake up near the summit and was associated with continued deflation of the summit. 

ERZ2 showing localized earthquake at 1:56 am May 29th, 2018

Pressure wave theory
My YouTube video which attempts to explain swings of seismic activity on pressure waves can be seen at: https://www.youtube.com/watch?v=pqgLhHuew6M

Please allow me to be the first to cast some doubt on that theory. Given the fact it appears I can tie three big events to sudden drops in measured tremor levels, then the dips in tremor level may not be due to pressure waves at all. Instead the dips in tremor level might be accounted for by large increases in lava flow volume. These large increases in flow volume mean tremor levels go down because no new expansion is necessary to make way for incoming lava.

Note: I am not saying pressure waves do not exist. In a rigid wall tube, if you introduce a viscus fluid at flow rate X you get a constant flow rate X at the outlet.


However, with a flexible tube, that same viscus fluid will interact with the walls of the tube and you will get pulses of high and low flow. A pump could be supplying a nearly perfectly uniform inflow, however tiny differences in pressure are amplified by interaction with the tube wall. The result is the outlet of a very long flexible tube looks like someone is turning the pump on and off.

There are at least three places that the flow could interact with a "flexible" membrane.

#1 At the summit the lake level can rise and fall and this would store pulsations in the form of potential energy.

#2 Level in the dike during transit may rise or fall.

#3 The pressure of the magmum could force apart flexible gaps because the earth isn't perfectly rigid.

Prediction
Current prediction as of May 29th, 6 pm HST. Tremor levels are back up again and this is especially true for ERZ2. Something is going to give again. Three things are possible:

1. A new fissure, either up or down rift,
2. Reopening of an existing fissure, or 
3. An earthquake that opens up more room for lava to expand into. 

Update May 29th, 8 pm HST.
I ran readings again. ERZ2 is now at the 2nd highest activity level I have yet measured since May 22nd, 2018. The 1st highest was just before Fissure 24 broke out. Two things should be noted:

A. Despite the high activity level at ERZ2, the eruption of Fissure 24, was not near Kapoho.
B. The USGS in a recent report stated they are watching deformation data in Kapoho and do not believe lava intrusion is occurring down rift.

Update May 29th, 12 midnight
Both ERZ1&2 peaked and are beginning to decline. Usually, KLUD has declined along with these two stations. However, instead of declining, KLUD has risen. I speculate this can be translated into a probability being now higher that an event, should it occur, will likely take place uprift as has always been expected.

ps You can review data on your own by following the links contained in this blog.