Real time seismometer using MPU6050/MPU9250
This program is a personal experiment to measure realtime Japan Meteorological Agency(JMA)'s instrumental seismic intensity scale (Shindo) with simplified algorithm, not fully following the procedures defined in reference [2].
No warranty for the precision of the intensity scale provided by this program.
Shindo (JMA's instrumental seismic intensity scale ) is only used in Japan and it is different from MSK or MM scale.[1]
- Shindo 2.5-3.4 is around 6-20 gal. Frequently observed in Japan.
- Shindo 3.5-4.4 is around 20-60 gal.
- Shindo 4.5-4.9 is around 60-110 gal. Get ready to protect yourself.
- Shindo 5.0-5.4 is around 110-200 gal. I have experienced this on the 14th floor in March 11th,2011. Extremely scary earthquake!
Shindo(Instrumental seismic intensity) and acceleration is quoted from [3]. Up to Shindo 2 is a noise level observed by this system.
IfF (Shindo: Instrumental seismic intensity scale by JMA ) is by definition,
IfF = 2.0 * log10( af ) + 0.94
where "af" is acceleration in gal, after filtering in the frequency domain for the entire time span using specified filter by JMA [2].
Max "af" acceleration corresponds 0.3sec duration is used to calculate max IfF for the entire shake. [2]
For example , IfF[]={3.2 , 1.2 , 2.5 , 2.2 , 3.1} is observed every 100msec , then let sort these values to {3.2,3.1,2.5,2.2,1.2} and the third value 2.5 is the max IfF Shindo for the earthquake.
Procedure [2] should be done for the entire waveform of the acceleration vector , but this program provides realtime IfF using a sliding buffer of 3 sec (30 samples) and simplified digital low pass/high pass filter in the time domein.
Since the filter in frequency domain specified in [2] is not easy to implement, software high pass filter at 0.2Hz and lowpass filter at 5Hz from sampling interval 10Hz are used to mimic the filter curve defined in [2]. High pass filter by Filters.h [5] also removes the gravity (980 gal), thanks to [4].
In this program , IfF at every 100msec are held for 3 sec in the sliding buffer (30 samples) and sorted every 100msec to find the third highest value, corresponding to 0.3sec rule in [2]. (thanks to ArduinoSort[7])
Max IfF during the last 30 sec is latched and published to MQTT server as Json format data, expecting Thingsboard running at MQTT port=2883 visualizes the Json data.( Note: default thingsboard opens port=1883 ) IfF_h is also calculated from horizontal acceleration.
Json format : {"press1": 1023.12,"temp1": 12.5,"IfF": 2.51 , "IfF_h":2.31}
- press1: barometric pressure in hPa from BMP388
- temp1: temperature in C from BMP388
- IfF: seismic intensity from 3D acceleration
- IfF_h: seismic intensity from horizontal acceleration
Acceleration is measured by MPU6050/MPU9250 placed horizontally. Since earthquake or volcanic erruption may affect barometric pressure , BMP388 is attached. Both devices are connected via I2C bus. If BMP388 is not attached , this program only sends IfF and IfF_h.
Simulation earthquake data BCJ-L1 and BCJ-L2 are available as an Exel format data from [8]. BCJ data is 10msec interval, one dimensional data , so the simulation data is given to X,Y and Z axis (half of X axis) at every 10msec. I have converted it to float bcjL1_wave[] and bcjL2_wave[] and run the simulation by #define SIMULATION
BCJ-L1,BCJ-L2 data are not included in this repository.
| data | BCJ-L1 | BCJ-L2 | comment |
|---|---|---|---|
| Shindo | IfF=5.5 | IfF=6.0 | See Ref.[6] page.8 |
| max IfF by this program | IfF=5.44 | IfF=5.93 | for 0.2Hz software high pass filter at sampling rate 10Hz |
The simulation result is not bad by chance.
The real earth quake was observed as IFf=2.65 in 23:34 2022-3-31 JST. According to JMA, its epicenter was Kameoka city , Kyoto pref. The magnitude was 4.3. https://www.data.jma.go.jp/multi/quake/quake_detail.html?eventID=20220331233814&lang=en https://earthquake.tenki.jp/bousai/earthquake/detail/2022/03/31/2022-03-31-23-34-14.html
Reported Shindo by JMA's observatory near my home was 2 which is trancated from Shindo (Instrumental seismic intensity scale ) , corresponding to 1.5 =< IfF < 2.5.
The observed result is not so bad.
First observation of the real earthquake
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ESP32devkit
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GY-521 MPU6050 or MPU9250 board wired on I2C bus.
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BMP388(optional) from Adafruit on I2C bus.
SDA = GPIO_NUM_21 , SCL = GPIO_NUM_22 LED and appropriate resister at GPIO_NUM_2 to indicate WiFi is ready
Bluttooth serial: acceleration(cm/s2) and IfF can be monitered by Bluetooth Serial terminal as "Seismo-BT-serial". Huge partition scheme in Arduino IDE is recommended when #define BTSERIAL is on.
Arduino board manager 1.0.6 / Arduino IDE 1.8.19
- [1] https://en.wikipedia.org/wiki/Japan_Meteorological_Agency_seismic_intensity_scale
- [2] https://www.data.jma.go.jp/eqev/data/kyoshin/kaisetsu/calc_sindo.html
- [3] http://www.daime.co.jp/gifujisin/data/skasokudo.html
- [4] https://create.arduino.cc/projecthub/mircemk/sensitive-mpu6050-seismometer-with-data-logger-9e6bf5
- [5] https://github.com/JonHub/Filters
- [6] http://www.bousai.go.jp/jishin/syuto/denkikasaitaisaku/2/pdf/siryou3.pdf
- [7] https://github.com/emilv/ArduinoSort
- [8] https://www.bcj.or.jp/download/wave/
- Copyright 2022 by coniferconifer
- Apache License
Barometric pressure surge by Tonga eruption in 20:39 Jan 15,2022 JST by AIRBENTO's BMP180.
The shock wave traveled 8000km from Tonga to Japan.