J-RISQ Report

2026-08-23 02:00 (UTC+9), SOUTHERN IBARAKI, 70km Depth, M 5.9 by JMA

I_s Distribution Maximum Observed I_s:5-

Seismic Intensity (I_s) distribution is estimated from the observed data (circles) of NIED K-NET, KiK-net, JMA, and local governments that had been collected by 2026/08/23 02:03:54.

Estimated I_s for Major Cities

Max. Obs. I_s	Histogram of Estimated I_s 1 2 3 4 5- 5+ 6- 6+ 7	Municipality Show All Data	Nighttime Population	Distance [km]
5-		Motegi,Haga,Tochigi	13,000	60
5-		Kawaguchi,Saitama	580,000	40
5-		Inashiki,Ibaraki	43,000	20
5-		Koto,Tokyo	490,000	44
5-		Urayasu,Chiba	170,000	42
4		Sumida,Tokyo	260,000	41
4		Edogawa,Tokyo	690,000	38
4		Toride,Ibaraki	110,000	10
4		Asahi,Yokohama,Kanagawa	250,000	76
4		Kasukabe,Saitama	230,000	31
4		Sakuragawa,Ibaraki	43,000	36
4		Shimotsuma,Ibaraki	43,000	24
4		Moka,Tochigi	80,000	49
4		Tsukuba,Ibaraki	230,000	9
4		Hokota,Ibaraki	48,000	41
4		Kasama,Ibaraki	76,000	42
4		Noda,Chiba	150,000	21
4		Ishioka,Ibaraki	77,000	27
4		Tsuchiura,Ibaraki	140,000	11
4		Ichikawa,Chiba	480,000	34
4		Sakura,Chiba	170,000	32
4		Kuki,Saitama	150,000	39
4		Chikusei,Ibaraki	100,000	36
4		Kanuma,Tochigi	98,000	71
4		Tatebayashi,Gumma	77,000	57
4		Nikko,Tochigi	83,000	88
4		Shiroi,Chiba	60,000	23
4		Hitachiomiya,Ibaraki	42,000	66
4		Shirosato,Higashiibaraki,Ibaraki	20,000	58
4		Atsugi,Kanagawa	220,000	90
4		Bando,Ibaraki	54,000	20
4		Haga,Haga,Tochigi	17,000	61
4		Omiya,Saitama,Saitama	120,000	43
4		Sammu,Chiba	53,000	51
4		Narita,Chiba	130,000	31
4		Kisarazu,Chiba	130,000	71
4		Katsushika,Tokyo	450,000	36
4		Shinjuku,Tokyo	330,000	49
4		Oyama,Tochigi	170,000	44
4		Hitachinaka,Ibaraki	160,000	58
4		Togane,Chiba	61,000	54
4		Mihama,Chiba,Chiba	150,000	39
4		Koga,Ibaraki	140,000	37
4		Kyonan,Awa,Chiba	8,000	101
4		Naka,Yokohama,Kanagawa	150,000	74
4		Koganei,Tokyo	120,000	63
4		Nakagawa,Nasu,Tochigi	17,000	82
4		Shibuya,Tokyo	220,000	52
4		Ichihara,Chiba	270,000	55
3		Minato,Tokyo	240,000	49
3		Kawasaki,Kawasaki,Kanagawa	220,000	63
3		Sosa,Chiba	37,000	52
3		Futtsu,Chiba	45,000	80
3		Matsudo,Chiba	480,000	29
3		Daigo,Kuji,Ibaraki	18,000	88
3		Katori,Chiba	77,000	37
3		Utsunomiya,Tochigi	520,000	65
3		Mobara,Chiba	90,000	65
3		Kashima,Ibaraki	68,000	48
3		Wakaba,Chiba,Chiba	150,000	40
3		Kamisu,Ibaraki	95,000	51
3		Tokorozawa,Saitama	340,000	61
3		Mito,Ibaraki	270,000	52
3		Ota,Gumma	220,000	73
3		Ome,Tokyo	140,000	78
3		Otsuki,Yamanashi	26,000	113
3		Kimitsu,Chiba	87,000	76
3		Isumi,Chiba	39,000	86
3		Hachioji,Tokyo	580,000	79
3		Hanno,Saitama	81,000	71
3		Hirata,Ishikawa,Fukushima	6,500	142
3		Yaita,Tochigi	33,000	91
3		Midori,Chiba,Chiba	130,000	48
3		Choshi,Chiba	64,000	71
3		Furudono,Ishikawa,Fukushima	5,300	128
3		Hiratsuka,Kanagawa	260,000	100
3		Sakura,Tochigi	45,000	77
3		Otawara,Tochigi	75,000	97
3		Kamogawa,Chiba	34,000	98
3		Kitaibaraki,Ibaraki	44,000	106
3		Higashiizu,Kamo,Shizuoka	13,000	166
3		Machida,Tokyo	430,000	78
3		Midori,Sagamihara,Kanagawa	170,000	82
3		Tamura,Fukushima	39,000	165
3		Miharu,Tamura,Fukushima	18,000	164
3		Yamakita,Ashigarakami,Kanagawa	11,000	116
3		Odawara,Kanagawa	190,000	118
3		Izu,Shizuoka	31,000	154
3		Koriyama,Fukushima	340,000	157
3		Hitachi,Ibaraki	190,000	83
3		Ichikawamisato,Nishiyatsushiro,Yamanashi	15,000	152
3		Ito,Shizuoka	68,000	146
3		Chonan,Chosei,Chiba	8,500	68
3		Kiryu,Gumma	110,000	82
3		Nishigo,Nishishirakawa,Fukushima	21,000	127
3		Katsurao,Futaba,Fukushima	20	177
3		Fujisawa,Kanagawa	420,000	91
3		Iwaki,Fukushima	350,000	136
3		Takahagi,Ibaraki	30,000	97
3		Shirakawa,Fukushima	61,000	125
3		Sukagawa,Fukushima	77,000	145
3		Kumagaya,Saitama	200,000	66
3		Higashimatsuyama,Saitama	91,000	63
3		Kanna,Tano,Gumma	2,000	107
3		Sano,Tochigi	120,000	57
3		Yabuki,Nishishirakawa,Fukushima	18,000	135
3		Minakami,Tone,Gumma	19,000	124
3		Nasushiobara,Tochigi	120,000	107
3		Minamiboso,Chiba	39,000	108
3		Matsuda,Ashigarakami,Kanagawa	11,000	113
3		Oshima,Tokyo	7,900	154
3		Kawagoe,Saitama	350,000	56
3		Yamatsuri,Higashishirakawa,Fukushima	6,000	101

The histogram shows frequency distribution of estimated I_s derived from interpolation of the observation with 250-m mesh. The daytime and nighttime correspond to 9:00-18:59 and 19:00-8:59, respectively. The distance is measured from the epicenter to the center of the municipality.

I_s Exposed-Population Estimates of Each City

5- or greater	5+ or greater
6- or greater Not Available	6+ or greater Not Available

Show All Data
Show All Data	5- or greater	5+ or greater	6- or greater	6+ or greater
Whole of Japan	2,000,000	5,000
Ibaraki Prefecture	100,000	5,000
Ishioka,Ibaraki	< 1,000
Ryugasaki,Ibaraki	20,000	< 1,000
Joso,Ibaraki	10,000
Toride,Ibaraki	50,000	5,000
Ushiku,Ibaraki	2,000
Tsukuba,Ibaraki	1,000
Moriya,Ibaraki	2,000	< 1,000
Chikusei,Ibaraki	< 1,000
Bando,Ibaraki	< 1,000
Inashiki,Ibaraki	< 1,000
Kasumigaura,Ibaraki	< 1,000
Sakuragawa,Ibaraki	5,000
Namegata,Ibaraki	< 1,000
Hokota,Ibaraki	< 1,000
Tsukubamirai,Ibaraki	20,000	< 1,000
Omitama,Ibaraki	< 1,000
Ibaraki,Higashiibaraki,Ibaraki	< 1,000
Miho,Inashiki,Ibaraki	< 1,000
Kawachi,Inashiki,Ibaraki	5,000
Tone,Kitasoma,Ibaraki	5,000
Tochigi Prefecture	5,000
Nasukarasuyama,Tochigi	< 1,000
Motegi,Haga,Tochigi	5,000
Saitama Prefecture	1,000,000
Minuma,Saitama,Saitama	< 1,000
Minami,Saitama,Saitama	5,000
Midori,Saitama,Saitama	20,000
Iwatsuki,Saitama,Saitama	5,000
Kawaguchi,Saitama	500,000
Kasukabe,Saitama	100,000
Soka,Saitama	200,000
Koshigaya,Saitama	200,000
Warabi,Saitama	50,000
Toda,Saitama	100,000
Wako,Saitama	< 1,000
Yashio,Saitama	50,000
Misato,Saitama	20,000
Satte,Saitama	< 1,000
Yoshikawa,Saitama	50,000
Sugito,Kitakatsushika,Saitama	2,000
Matsubushi,Kitakatsushika,Saitama	20,000
Chiba Prefecture	50,000
Ichikawa,Chiba	5,000
Noda,Chiba	< 1,000
Narita,Chiba	< 1,000
Sakura,Chiba	1,000
Kashiwa,Chiba	2,000
Yachiyo,Chiba	< 1,000
Abiko,Chiba	5,000
Urayasu,Chiba	50,000
Yotsukaido,Chiba	< 1,000
Inzai,Chiba	1,000
Shisui,Imba,Chiba	< 1,000
Sakae,Imba,Chiba	< 1,000
Tokyo Prefecture	1,000,000
Taito,Tokyo	20,000
Sumida,Tokyo	200,000
Koto,Tokyo	50,000
Kita,Tokyo	100,000
Arakawa,Tokyo	100,000
Itabashi,Tokyo	10,000
Adachi,Tokyo	500,000
Katsushika,Tokyo	2,000
Edogawa,Tokyo	100,000
Kanagawa Prefecture	200,000
Kanagawa,Yokohama,Kanagawa	5,000
Hodogaya,Yokohama,Kanagawa	< 1,000
Kohoku,Yokohama,Kanagawa	50,000
Asahi,Yokohama,Kanagawa	10,000
Midori,Yokohama,Kanagawa	50,000
Seya,Yokohama,Kanagawa	5,000
Aoba,Yokohama,Kanagawa	20,000
Tsuzuki,Yokohama,Kanagawa	100,000
Nakahara,Kawasaki,Kanagawa	< 1,000
Takatsu,Kawasaki,Kanagawa	20,000
Miyamae,Kawasaki,Kanagawa	20,000
Yamato,Kanagawa	1,000

The summation of the exposed population for each city does not necessarily equal to that of the prefecture or whole of Japan.

Major Historical Damaging Earthquakes in This Region

Year	Region	M	Damage
1921	Southern Ibaraki	7.0	Ryugasaki Earthquake,Minor damage in Chiba and Ibaraki such as damage to houses and roads.
1922	West coast, Chiba	6.8	Uragasuido Earthquake,1 dead in Tokyo, 1 dead in Yokohama, Kanagawa. Houses were damaged.
1923	Western Kanagawa	7.9	Kanto Earthquake,The maximum amplitude of 14-20 cm was observed in Tokyo. Over 105,000 dead or missing, over 109,000 houses collapsed, 102,000 partially destroyed, over 212,000 destroyed by fire. Many landslides. Tsunamis struck the coast of Kanto. Wave heights were 12 m in Atami, Sizuoka; 9.3 m in Aihama, Chiba.
1931	Northern Saitama	6.9	Nishi Saitama Earthquake,16 dead, 207 collapses (76 houses and 131 non-residential houses).
1949	Northern Tochigi	6.2	Imaichi Earthquake,10 dead, 290 houses collapsed, 2,994 partially destroyed, 618 non-residential houses collapsed. Many masonries were damaged. Many landslides were observed.
1987	E Off Chiba	6.7	2 dead, 161 injured in Chiba. 16 houses collapsed and over 70,000 partially destroyed. Many roads damaged.
2011	Hamadori, Fukushima	7.0	The crustal earthquake with normal faults, induced by the 2011 off the Pacific Coast of Tohoku Earthquake. 4 dead, 10 injured (as of March 2016). Maximum Is was 6-.
2012	E Off Chiba	6.1	The crustal earthquake with normal faults, induced by the 2011 off the Pacific Coast of Tohoku Earthquake. 1 dead, 1 injured. Maximum Is was 5+.

Reference: National Astronomical Observatory of Japan, Chronological Scientific Tables, Maruzen, (2017) *partially extracted

Seismic Hazard Information of J-SHIS

J-SHIS is a Web service by NIED, to help prevent and prepare for earthquake disaster by providing a public portal for seismic hazard information across Japan.

I_s Distribution of 2% Probability of Exceedance in 50 Years

SI Distribution of 2% Probability of Exceedance in 50 Years

I_s Distribution of Return Period of 50,000-year

R-20260823020101-0085-00001

J-RISQ (http://www.j-risq.bosai.go.jp/)

Updated: 2026-08-23 02:04:13 (UTC+9) Ver.4

Is Distribution Maximum Observed Is:5-

Estimated Is for Major Cities

Is Exposed-Population Estimates of Each City

Major Historical Damaging Earthquakes in This Region

Seismic Hazard Information of J-SHIS

I_s Distribution Maximum Observed I_s:5-

Estimated I_s for Major Cities

I_s Exposed-Population Estimates of Each City