Mexico_M7

地球内部構造と地震波とくに，P波の影の地震 Y.Okamoto 2026-07-21

Inner earth and seismic waves, particularly in the "P-wave Shadow Zone".
Comparisonn of Seismograms: ours and the IRIS sites

We will explain why the diffractice phases are observed in real seismograms using Ray-paths and inner earth wave simulation.

I would like to express my gratitude to Mr. Niwat and Mr. Pao at PCSHS Mukdahan, who always maintain our seismometers.

How to get IRIS data: http://seagull.stars.ne.jp/2026_Thailand/Epi-Center/Epi-Center.html

１．Mexico M7.3
https://earthquake.usgs.gov/earthquakes/eventpage/us7000t1bu/executive

Nomenclature source: https://www.isc.ac.uk/standards/phases/

2. P-wave Shdow-Zone from a textbook for high-school

3.Comparison of our seismograms and IRIS sites.

At Kashihara Osaka, Japan vs Matsushiro Nagano, Japan

You can download the original images from the following.

At PCSHS Mukdahan, Thailand vs Chiang Mai, Thailand

Both signals show weak P-Diffractive phases.

4. Why diffracting P is appeared. from our Prem simulation.

Our original simulation is here.
http://seagull.stars.ne.jp/Inner_Earth/Prem_uv2.mp4

5. More Details about Seismic Phases Nomenclature are at https://earthquake.tmd.go.th/file_downloads/wave_interpret/PartChapter%202.pdf

From Peter Bormann, E. Robert Engdahl, and Rainer Kind (2012)