That "worn down house" might be good until "upper 6". Beyond that it all depends on when it was built and the associated construction standards at the time.
Source: https://isec-society.org/ISEC_PRESS/ASEA_SEC_03/pdf/St-5_v5_...
It all stems from an earthquake in 1923 in Yokohama which killed 140,000. Since then Japan's has over time developed some of the strictest seismic standards.
Two issues: 1. If you're making this choice during an earthquake, "outside" is often not a grassy field but rather the fall zone for debris from whatever building you're exiting. 2. If the earthquake is big/strong enough that you're in any real danger of building level issues, the shaking will be strong enough that if you try to run for the outside you're very likely to just fall and injure yourself.