Comparison

J vs Moon Book

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

J

This app provides official earthquake hazard maps for Japan, allowing users to view predictions of ground shaking intensity. It offers detailed information based on location and displays fault lines and seismic activity models.

Highlights
  • View national earthquake hazard maps
  • Zoom, pan, and adjust map transparency
  • Display probabilistic seismic hazard maps
  • Show surface and deep ground maps
  • View earthquake source fault locations
  • Display seismic activity models
  • Show location-specific earthquake probabilities
Features
Read full description

地震ハザードステーションJ-SHISの公式アプリケーションです。 J-SHISは全国地震動予測地図を表示するiPhone/iPad用公式アプリケーションです。J-SHISを手軽にスマートフォンで見ることができます。 ○全国地震動予測地図※の表示○ 現在公開している最新の全国地震動予測地図を表示することができます。地図は拡大・縮小、移動、透過率の変更を行うことができます。 ・確率論的地震動予測地図(30年震度6強以上となる確率) ・確率論的地震動予測地図(30年震度6弱以上となる確率) ・確率論的地震動予測地図(30年震度5強以上となる確率) ・確率論的地震動予測地図(30年震度5弱以上となる確率) ・長期間平均ハザード(再現期間10万年相当) ・表層地盤地図 ・深部地盤地図 ・想定地震地図 ※「全国地震動予測地図」は、将来日本で発生する恐れのある地震による強い揺れを予測し、予測結果を地図として表したものです。 ○GPSを利用した現在位置周辺の表示○ 地図表示範囲をGPSを利用して現在位置周辺にすることができます。 ○地点情報の表示○ 指定した地点で30年間に震度6弱以上の揺れに見舞われる確率や、表層地盤増幅率、地震ハザードカルテを表示することができます。 ○震源断層の位置と地震活動モデルの表示○ 地図上に主要活断層帯の位置・形状を表示することができます。震源断層をタップすると地震活動モデル(平均ケース)を表示します。

About

Moon Book

This app visualizes lunar eclipses, showing viewing times and directions from your location. Plan your observations by setting specific locations and previewing eclipse phases.

Highlights
  • Lunar eclipse viewing times
  • Direction of eclipse visibility
  • Location-specific eclipse phases
  • Pre-set observing locations
  • Overseas eclipse start times
  • Thumbnail images of eclipse phases
Features
Read full description

The Moon Book App clearly shows you when and from which direction eclipse of the moon can be viewed. The time of beginning or ending penumbral eclipse is simultaneous around the country but a place of beginning total eclipse differs from pace to place. The Moon Book will show you the phases of the moon eclipse at your place. You will be able to set up any observing place beforehand if the moon eclipse star chart is selected. When you move to a distant place for observing the moon eclipse, you will be able to know in advance a place where the Earthfs shadow starts hiding the moon. You will be able to check a start time of the moon eclipse overseas also. Tapping on the moon icon at the upper left corner of the star chart will show you thumbnail images of the phases of the moon eclipse at regular intervals. The interval of the thumbnail images can be changed.

Screenshots

J4 screens
Moon Book4 screens

Verdict

The call

The clearest difference is review sentiment: Moon Book at 90% against J's 33%. Moon Book also leads on update cadence (every 6 months vs every 13 months) and iOS requirement (12.0 vs 15.0). On price, ads, in-app purchases and monetization model there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

J ships an update every 13 months, Moon Book every 6 months. The most recent releases landed on November 6, 2026 and November 1, 2026 respectively.

Scorecard3 real differences · 5 level
J versus Moon Book: the parameters behind the verdict, then further details
ParameterJMoon Book
PriceFreeFree
Positive reviews33.3% of reviews90.0% of reviews — better
Update frequencyEvery 13 monthsEvery 6 months — better
AdsNoNo
In-app purchasesNoNo
MonetizationFreeFree
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.012.0 — better
Further details — not scored
Size9 MB22 MB
Age rating4+4+
DeveloperNational Research Institute for Earth Science and Disaster PreventionVixen Co.,Ltd.

Customer experience

J

Written reviews9 reviews
Positive33.3%
Neutral22.2%
Negative44.4%

Moon Book

Written reviews10 reviews
Positive90.0%
Neutral10.0%
Negative0.0%

In-app purchases

None

J

No in-app purchases

None

Moon Book

No in-app purchases

Questions

Is J free?
J is free to download, with no in-app purchases.
Is Moon Book free?
Moon Book is free to download, with no in-app purchases.
Do J or Moon Book have ads?
Neither J nor Moon Book shows ads.
Which is updated more often, J or Moon Book?
J ships an update every 13 months, and Moon Book every 6 months. Most recently, J was updated on November 6, 2026 and Moon Book on November 1, 2026.

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