JMA scale

The JMA scale ( Japanese 気 象 庁 震 度 階級 , kishō-chō shindo kaikyū , dt. "Earthquake strength classes according to Japan Meteorological Agency (JMA)") is the intensity scale used by the JMA and the Taiwanese CWB ( Central Weather Bureau ) for earthquakes .

A first scale with four intensity levels was developed by the JMA in 1884. After several extensions, a new scale was developed by the JMA in 1951 on the basis of the Ōmoriskale developed by Fusakichi Ōmori in 1900 , the seven levels of which are based on limit values ​​for the maximum ground acceleration . The JMA has been using the scale in its current form since 1996.

Unlike magnitude scales , e.g. B. the often cited Richter scale , intensity scales such as the JMA scale, the EMS scale or the Mercalli scale describe the effects of an earthquake on the surface and can therefore show different strengths for a single earthquake in different locations. They should therefore not be confused with magnitude scales, especially not with the JMA magnitude scale .

In the case of earthquakes in Japan, the earthquakes are now recorded on the basis of automatic measurements and the intensity is determined by frequency-filtering the accelerations and converting them into a "measured earthquake strength " ( 計 測 震 度 , keisoku shindo ). The calculated values ​​are transferred to the JMA scale according to defined limit values. Then the JMA (and, in the case of stronger earthquakes, also the mass media) will publish maps with intensities for all measuring stations in addition to the magnitude.

The individual levels ( shindo kaikyū ) of the JMA scale are described as follows:

JMA scale

Shindo (intensity)	People	Situation in buildings	Situation outdoors	Wooden houses	Reinforced concrete houses	Electricity, gas, water lines	Floor and slopes
0	imperceptible
1	noticeable for some people
2	Noticeable for many people, can wake sleepers	Ceiling lamps and other hanging objects can swing a little
3	Noticeable to most people, causes fear in some people	Dishes on shelves can rattle	Power lines vibrate a little
4th	triggers widespread fear, some people seek protection, most sleepers wake up	Hanging objects swing considerably, dishes rattle, unstable decorative objects ( Japanese 置物 , okimono , objects in a tokonoma ) can fall over	Power lines vibrate strongly, noticeable even for people walking, some drivers notice the tremor
5 弱 5-jaku ("weak 5")	many people seek protection, some people struggle to move	Hanging objects oscillate considerably, dishes and books can fall from shelves, many unstable items of jewelry fall over, and furniture can slip	Window panes can break and fall, telegraph and electricity poles wobble visibly, unreinforced stone walls can collapse, and occasionally road damage	Occasionally damaged walls or pillars in houses that are poorly protected against earthquakes	cracks in the walls occasionally in houses with little earthquake protection	In some houses safety shutdown of the gas supply, isolated failure of the water supply due to line damage ( power failure for individual households)	can cause cracks in soft ground, and occasionally rock falls and minor landslides in mountainous areas
5 強 5-kyō ("strong 5")	triggers panic, many people struggle to move	Dishes and books fall off shelves, televisions can fall off the frame, heavy furniture such as chests of drawers can fall over, occasionally warped doors cannot be opened, sliding doors can fall out	many unreinforced stone walls collapse, poorly set up machines can fall over, many tombstones fall over, driving vehicles becomes difficult and many stop	Houses that are poorly protected against earthquakes can be crooked due to damaged walls or pillars	in houses with weak earthquake protection there are sometimes large cracks in the walls, struts and pillars, and occasional cracks in earthquake-proof houses too	Damage can occur in household gas supply lines and main water pipes (failure of the water and gas supply in some areas)	can cause cracks in soft ground, and occasionally rock falls and minor landslides in mountainous areas
6 弱 6-jaku ("weak 6")	standing upright is difficult	Unsecured heavy furniture slips or falls over, and many doors can no longer be opened	window panes and bricks are often damaged and fall off	Houses that are poorly protected against earthquakes can collapse, and houses that are protected against earthquakes occasionally suffer damage to walls or pillars	Walls and pillars can sometimes collapse in houses that are not well protected against earthquakes, and large cracks in walls, struts and pillars can also occur in earthquake-proof houses	Damage to household gas pipes and main water pipes (failure of electricity, water and gas supply in some areas)	can trigger crevices and landslides
6 強 6-kyō ("strong 6")	It becomes impossible to stand still, only crawling locomotion is possible	almost all unsecured heavy furniture slips or falls over, doors can pop out and be thrown away	Window panes and bricks are widespread damaged and fall down, unreinforced stone walls collapse widespread	many houses that are weakly protected against earthquakes collapse, and houses that are protected against earthquakes often suffer damage to walls or pillars	Houses that are poorly protected against earthquakes can collapse, and walls and pillars can also collapse in many earthquake-proof houses	Damage to main gas lines and waterworks possible (in some areas power outages, widespread failure of the water and gas supply)	can trigger crevices and landslides
7th	Targeted locomotion becomes impossible due to the quake	almost all furniture is being moved, some flying through the air	almost all window panes and bricks are damaged and fall down, even reinforced stone walls can collapse	Some earthquake-proof houses are also crooked or seriously damaged	Some earthquake-proof houses are also crooked or seriously damaged	(widespread failure of electricity, gas and water supplies)	large crevices, landslides and landslides and even changes in topography are possible

Intensity 7

The highest intensity on the JMA scale was introduced in Fukui Prefecture in 1949 after an earthquake the previous year with over 35,000 buildings destroyed. It was first reached in the 1995 Kobe earthquake . Although a lower intensity was measured by measuring devices, based on the devastation, the earthquake was given as intensity 7. Shindo 7 was hit for the second time on October 23, 2004 by a 6.8 magnitude earthquake in Niigata Prefecture. The Tohoku earthquake in 2011 also reached Shindo 7 at a measuring station. The highest intensity was again reached in the earthquake in Kumamoto in April 2016. Both one of the foreshocks on April 14th and the main quake with a magnitude of 7.0 on April 16 reached Shindo 7. The 2018 Hokkaido earthquake also reached intensity 7 on the Shindo scale in the municipality of Atsuma .

Other earthquakes that occurred prior to the introduction of Shindo 7 have reached that magnitude. These include the 1923 Kanto earthquake . In addition, some earthquakes in areas that are not equipped with gauges may have reached intensity 7, including the 2008 Iwate earthquake and the 2007 Niigata-Chuetsu earthquake . The following table lists some more recent earthquakes for which an intensity of 7 was determined locally.

Date (local time)	Places with intensity 7	prefecture	Magnitude ( M jma )
September 6, 2018	Atsuma (Shikanuma)	Hokkaido	6.7
April 16, 2016	Mashiki (Miyazono), Nishihara (Komori)	Kumamoto	7.3
April 14, 2016	Mashiki (Miyazono)	Kumamoto	6.5
March 11, 2011	Kurihara (Tsukidate)	Miyagi	9.0
October 23, 2004	Nagaoka (Higashikawaguchi)	Niigata	6.8
January 17, 1995	Awaji , Kobe , Ashiya , Nishinomiya , Takarazuka	Hyogo	7.3

Individual evidence

1. ↑ Integrated practical course III: Earthquake (Experiment D), Figure 2.6: Comparison of the frequently used intensity scales. Swiss Seismological Service (SED)  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.  
2. ↑ Calculation on the JMA website ( Memento of the original from September 17, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (Japanese)  
3. ↑ Description of the instruments and the calculation method (English)
4. ↑ JMA earthquake archive with records of all Japanese earthquakes of the last week (English)
5. ↑ Table on the JMA homepage (Japanese)
6. ↑ 気 象 庁 Japan Meteorological Agency: 気 象 庁 ｜ 震 度 デ ー タ ベ ー ス 検 索 （地震 別 検 索 結果）. Retrieved September 9, 2018 (Japanese).