Shootings affecting many people (ie mass shootings) in America aren’t common, and are over very quickly. Notification apps would not change the outcomes.
Earthquakes in Japan are a fact of life, and affect many many people very often. Mass shootings anywhere (USA included) are rare, freak occurrences, that involve small numbers of people.
Additional fearmongering over the very tiny risk from gun violence in the US actually makes the problem worse, not better. The mass media already does more than enough of that.
When you look at a source like Gun Violence Archive, they report many incidents where there is no loss of life as "mass shootings", and they also report many incidents of criminal conflict as mass shootings. The reality is that if you are not involved in criminal activity, you are vanishingly unlikely to be shot by someone else in the United States.
In my neighborhood I hear gunshots almost every night. There were several shootings within a block of my house just in the last six months, including one where patrons of the nearest bar had to run and hide in the walk-in freezer while two idiots shot at each other (and both missed). Often times I hear shots and check the police log and can't even find a reference to them.
According to the Gun Violence Archive[0], the US has averaged 2 mass shootings a day over the last three years - less common than earthquakes in Japan, but far from being rare or a freak occurrence.
A report from the FBI on "active shooter incidents" from 2022 indicate between 30 and 70 occur in a year. In 2022, there were 13 that met the Federal criterion for a "mass killing": 3 or more killed.
The reason these statistics are so different from what GVA provides is because the FBI is looking at the kinds of incidents that present a risk to a member of the general public, otherwise going about their business: they exclude self-defense incidents, gang wars, drug deals gone bad, and domestic disputes.
GVA, however, defines any incident with 4 or more injured or killed with a gun as a "mass shooting", which technically includes even some gun range accidents. Many of the incidents they report do not involve any deaths at all. Most of the incidents they report are criminal conflict, not the kind of terrorist attacks people are thinking of when the term "mass shooting" is used. The risk profile of criminal conflict is very different from that of a terrorist attack, generally, since being involved in crime is a significant predisposing factor.
Using GVA statistics to get a sense of one's likelihood of injury from guns in the USA, as a basis for a comparison to natural disasters, greatly overestimates the likelihood of firearms related injury (unless you are a gang member or regularly engage in robbery, burglary, &c).
I am using the term in the layperson sense. In that sense, there are generally only 1-3 events per year, affecting fewer than 500 people in a country of 350M. (Most of the gun murders in the US are not from mass shootings.)
Significant earthquakes in Japan occur at least 5-10x more often, and affect 2-4 orders of magnitude more people.
Websites like the one you linked use a definition of the term much different than the one commonly used by everyday people.
Earthquakes in Japan are a fact of life, and affect many many people very often. Mass shootings anywhere (USA included) are rare, freak occurrences, that involve small numbers of people.
Additional fearmongering over the very tiny risk from gun violence in the US actually makes the problem worse, not better. The mass media already does more than enough of that.