- The earthquake site is almost equidistant from the interferometers, and the front of the seismic wave could arrive to interferometers about the same time and exactly as registered (taking in account some indefinites in the wave paths inside the Earth crust).

I do not mean any direct impact of seismic waves to suspended mirrors. They have good immunity to interference from seismic waves, but the seismic wave had direct influence to length of arms of the interferometers, and they registered this short-period change of the length.

Dear Ivan,

why do you affirm that the earthquake site is almost equidistant from the two LIGO interferometers ? If you calculate P-wave travel times (the fastest waves travelling in the earth) using right coordinates for the earthquake and LIGO observers you will get seconds and not 10 ms. The two interferometers recorded simultaneously (7 ms delay) the wave. Moreover, waveforms are self-similar. Never seen an earthquake that is able to give the same waveform at two receivers 3000 km far (and in the 60 - 250 Hz frequency band). 

Dear Alessandro,

I consider the great circlee distances from Hanford and Livingston (differing to 97 km) as estimates for really unknown paths of P-Waves. It might happen so that real Earth' crust structure along the refracted P-wave paths differs in a such way, that the arrival time will correspond to 7ms delay. The P-wave waveforms registered at Hanford and Livingston have specific shape and look similar due to:

1. Effect of P-Wave front transformation due to dispersion in the Earth' crust layers with different speed, causing low frequencies to arrive earlier than higher frequencies.

2. Frequency filtering properties of the LIGO interferometers.

3. Rather high level of residual noise, shown in the third line of FIG.1 in the main paper of LIGO Collaboration.

Thanks for your comments.

The reason for the noise does not matter. Noise level sets the uncertainty in comparing waveforms.

Dear Ivan

the great circle path is not the  P-wave path. The teleseismic P-wave goes deep into the earth and comes back almost vertical. Could you provide to me coordinates of the earthquake and magnitude ? I will calculate P-wave travel times and will tell you about. A 10000 km far earthquake is not able to generate dispersed high frequencies. The incidence angle for teleseismic earthquake is sub-vertical and P-waves cannot be dispersed at the receiver or travel horizontally as surface waves. Keep in mind that the earth is a powerful filter for high-frequency seismic waves, and local noise easily overcome the null high frequency signal from distant earthquakes 

The only earthquake close to 9:50 with magnitude greater than M-4.5 is located in China by USGS. No earthquakes in Turkey in the European bullettin. This means that your eqk is a small local one. However, I used your coordinates without including earthquake depth and magnitude and considering TauP travel times for the fastest waves the delay is larger than second. For other seismic phases the delay increases. 

Dear Alessandro,

The link in my initial message leads to the eartquake data:

Magnitude ML 2.3

Region WESTERN TURKEY

Date time 2015-09-14 09:35:43.8 UTC

Location 40.08 N ; 28.56 E (40°04'48"N, 28°33'36"E)

Depth 5 km

Livingston, LA 30°33′46.42″N90°46′27.27″W

Hanford, WA 46°27′18.52″N119°24′27.56″W

09:50:45 UTC

The earthquake has a really small magnitude, however LIGO itself is a supersensitive equipment, which has not been designed for seismologic tasks. Though, laser interferometry techinique is considered to be the most advanced for seismology:

http://people.na.infn.it/~garufi/Pubblicazioni/Paper%20Velocimeter%20SPIE%20RS07.pdf

http://onlinepresent.org/proceedings/vol29_2013/32.pdf

I understand that P-Wave travel inside the Earth crust, that is shown at the other link in my initial message. Though any comments from specialists regarding plausibility of the P-Wave being registered by measuring channel  of LIGO interferometers are welcome. It would be nice if somebody could apply available Earth crust models for the task of calculating P-Waves paths to Livingston and Hanford.

Speaking about registration of P-Wave, I do not mean the sensitivity of seismic isolation devices, which detect and then immediately offset ground vibrations, keeping LIGO’s components, such as its mirrors, at rest. The LIGO laser interferometer is considered being more sensitive than the seismic isolation equipment, capable to discover very low P-Wave signal at the sensibility level of aLIGO.

>Knowing that noise does not have the seismic origin is "information" that has to be added to the evaluation of the whole event.

- Sure. One may also see a 35 Hz splash at noise diagram on the FIG.3 in LIGO paper. May this have any relation to seismics?

Thanks!

Here below the test made using your coordinates for the event, for the P-wave and S-wave arrival at LIV (Livingston) and HAN (Hanford). I do not believe a M=2.3 eqk will propagate so far. However in any case HANFORD should record P-waves almost 4 s before LIVINGSTON. Moreover if the eqk origin time is correct your P-waves should arrive at 9:48:39 s and S-waves more than 10 min later. 

The earth model used for calculation is AK135.  

bash-3.2$ ./testLIGO.py

Building obspy.taup model for './ak135.tvel' ...

Station== LIV

epi_dist== 9998.84211206

deg== 89.9217474555

2 arrivals

P phase arrival at 780.187 seconds

S phase arrival at 1433.304 seconds

arrP.time=... 780.187435464

arrS.time=... 1433.30436524

Station== HAN

epi_dist== 9906.16950748

deg== 89.0883226997

2 arrivals

P phase arrival at 776.298 seconds

S phase arrival at 1425.528 seconds

arrP.time=... 776.297568306

arrS.time=... 1425.5277238

For sake of truth here below all the 35 seismic phases at the two stations, from this we learn that it's impossible to get the same waveform at the two stations from the eqk

Building obspy.taup model for './ak135.tvel' ...

Station== LIV

epi_dist== 9998.84211206

deg== 89.9217474555

35 arrivals

P phase arrival at 780.187 seconds

PcP phase arrival at 781.437 seconds

pP phase arrival at 781.860 seconds

sP phase arrival at 782.454 seconds

PP phase arrival at 992.779 seconds

PKiKP phase arrival at 1076.604 seconds

pPKiKP phase arrival at 1078.321 seconds

sPKiKP phase arrival at 1078.906 seconds

SKiKP phase arrival at 1291.676 seconds

SKS phase arrival at 1411.597 seconds

pSKS phase arrival at 1413.839 seconds

sSKS phase arrival at 1414.439 seconds

SKKS phase arrival at 1424.700 seconds

S phase arrival at 1433.304 seconds

pS phase arrival at 1435.442 seconds

sS phase arrival at 1436.071 seconds

ScS phase arrival at 1437.526 seconds

SP phase arrival at 1498.369 seconds

SP phase arrival at 1498.724 seconds

SP phase arrival at 1498.890 seconds

PS phase arrival at 1499.034 seconds

PS phase arrival at 1499.378 seconds

PS phase arrival at 1499.548 seconds

SS phase arrival at 1790.730 seconds

PKIKKIKP phase arrival at 1827.205 seconds

PKKP phase arrival at 1831.562 seconds

SKIKKIKP phase arrival at 2042.325 seconds

PKIKKIKS phase arrival at 2042.909 seconds

SKKP phase arrival at 2050.423 seconds

PKKS phase arrival at 2051.009 seconds

SKIKKIKS phase arrival at 2257.805 seconds

SKKS phase arrival at 2268.962 seconds

PKIKPPKIKP phase arrival at 2321.371 seconds

SKIKSSKIKS phase arrival at 3185.402 seconds

SKSSKS phase arrival at 3189.251 seconds

Station== HAN

epi_dist== 9906.16950748

deg== 89.0883226997

31 arrivals

P phase arrival at 776.298 seconds

PcP phase arrival at 777.749 seconds

pP phase arrival at 777.970 seconds

sP phase arrival at 778.563 seconds

PP phase arrival at 986.120 seconds

PKiKP phase arrival at 1075.219 seconds

pPKiKP phase arrival at 1076.937 seconds

sPKiKP phase arrival at 1077.521 seconds

SKiKP phase arrival at 1290.239 seconds

SKS phase arrival at 1406.712 seconds

pSKS phase arrival at 1408.952 seconds

sSKS phase arrival at 1409.552 seconds

SKKS phase arrival at 1418.464 seconds

S phase arrival at 1425.528 seconds

pS phase arrival at 1427.662 seconds

sS phase arrival at 1428.292 seconds

ScS phase arrival at 1430.615 seconds

SP phase arrival at 1488.526 seconds

PS phase arrival at 1489.191 seconds

SS phase arrival at 1778.644 seconds

PKIKKIKP phase arrival at 1828.658 seconds

PKKP phase arrival at 1833.625 seconds

SKIKKIKP phase arrival at 2043.732 seconds

PKIKKIKS phase arrival at 2044.316 seconds

SKKP phase arrival at 2052.329 seconds

PKKS phase arrival at 2052.915 seconds

SKIKKIKS phase arrival at 2259.173 seconds

SKKS phase arrival at 2270.779 seconds

PKIKPPKIKP phase arrival at 2322.926 seconds

SKIKSSKIKS phase arrival at 3186.855 seconds

SKSSKS phase arrival at 3191.313 seconds

Thanks to ObsPy guys. Here below a graph of possible travel paths for seismic waves

>True. But then 2015-09-14 09:35:43.8 UTC earthquake would need to be THE only one that day to stand out of the (other) noise otherwise caused by many other tectonic motions of the planet.

LIGO employs 10 ms window to filter out simultaneous events at Hanford and Livingston. For slow P-Waves this means that earthquake should be approximately equidistant from both interferometers; P-Wave travel time should correspond to real velocity band of P-Waves; the earthquake shouldn't occur in the shadow zone of P-Wave (100°-140°); the P-Way need to go through considerable distortion in the Earth crust layers, - a lot of limitations, which were fulfilled for the Turkish earthquake.

>Each aLIGO instrument detected GW event independently.

- Nothing special for similar laboratories approximately equidistant from the earthquake.

>There is another way to test and reject the earthquake hypothesis. The frequency increase of the signal was 10-fold towards the peak. This is highly unusual property to have originated from an earthquake.

I do not know all the technical details. Whether the pike is related to the event, or it was available a long time before? Also the issue, one should take in account, is orientation of the P-Wave front in relation to interferometer arms. In case the wave is not going strictly along the arm, the speed of transient compression wave along the arm should increase. At acute angle it may increase significantly, comparing to omnidirectional seismic detector. 

>The only earthquake close to 9:50 with magnitude greater than M-4.5 is located in China by USGS. 

>However, I used your coordinates without including earthquake depth and magnitude and considering TauP travel times for the fastest waves the delay is larger than second.

Thank you very much! I also tested Chinese eqk before, but it was not equidistant from LIGO. Two questions arise. How accurate, trustworthy and steady is the Earth crust model used for the calculation? Can we trust to the Turkish eqk coordinates?

The earth is not homogeneous - it is impossible to get the same ground motion  for so distant observatories in a so high frequency range. This is the point. And antropic local vibrations all around the observatories are for sure  strongest than your tiny earthquake. And this is true for any other earthquake recorded by worldwide networks that day. Free to believe in something else (e.g. aliens hidden in the deep interior). I do not reply further.

Dear Aleš Kralj and Alessandro Vuan, thanks for your help! 

I've found estimations for the AK135 accuracy, it looks quite reliable.

ftp://ftp.isc.ac.uk/pub/iwref/docs/Greece.pdf

>antropic local vibrations all around the observatories are for sure strongest than your tiny earthquake

Any local vibrations are being compensated by seismic isolation devices and also have no chance to occure simaltaneously at both stations. Though, Alessandro, if AK135 is reliable for calculation of teleseismic P-waves arrival time for the case of  GW150914, then, you are right.

Dear Ivan,

Congratulation for question! You have made again an excellent observation… All Earthquakes are producing fluctuation in gravitational waves… I do not know if the LIGO used this small Earthquakes… Perhaps they did… They wanted to not be observed by “outsider scientist”… These was a very small Earthquakes and thanks for you it can be verified!  For more information:

I have two papers in connection to this subject

https://www.researchgate.net/publication/313632704_AZ_ELMELETI_TUDOMANY_KENYES_JELENSEGE

(it is in Hungarian, but I have attached English abstract, and an English comment)

https://www.researchgate.net/publication/277364319_Tenyekkel_igazolhato_a_gravitacio_valos_oka

(the tittle: The real cause of gravity can be demonstrated with facts; here explained real cause of gravity which permit explanation of your question and permit explanation of process discovered by me: “planet-erosion”

 http://planeterosion.blogspot.hu/

Onto base of this theory I have predicted a strong Earthquakes in Iran in 2015 December

https://www.researchgate.net/post/An_old_question_that_is_still_fresh_Is_gravity_a_Newtonian_force_or_Einstein_space-time_curvature/104

“The actual condition (the position of Earth and Moon) are favorable for a major earthquakes in Hemisphere North 5-30;  ASIA… bigger than 6.5 magnitude in the next 2-3 days (23-24 December)

(An old question that is still fresh: Is gravity a Newtonian force or Einstein space-time curvature?. Available from: https://www.researchgate.net/post/An_old_question_that_is_still_fresh_Is_gravity_a_Newtonian_force_or_Einstein_space-time_curvature/104 [accessed May 9, 2017].”)

“The even in Afganistan was near prediction was :

M 6.2 - HINDU KUSH REGION, AFGHANISTAN - 2015-12-25 19:14:47 UTC”

http://www.emsc-csem.org/Earthquake/earthquake.php?id=478705

https://en.wikipedia.org/wiki/List_of_earthquakes_in_2015

 An old question that is still fresh: Is gravity a Newtonian force or Einstein space-time curvature?. Available from: https://www.researchgate.net/post/An_old_question_that_is_still_fresh_Is_gravity_a_

Best Regards,

Laszlo

Newtonian_force_or_Einstein_space-time_curvature/105 [accessed May 9, 2017].

Research AZ ELMÉLETI TUDOMÁNY KÉNYES JELENSÉGE

Article Tényekkel igazolható a gravitáció valós oka