The magnitude of the second earthquake, is approximately 5.84.
To find the magnitude of the second earthquake, we'll use the given moment magnitude scale (MMS) formula and the information about the earthquakes' energies. The MMS formula is:
![\[ M = (2)/(3) \log\left((E)/(E_0)\right) \]](https://img.qammunity.org/2024/formulas/mathematics/high-school/tp9cu83f4nd3lcg6m96dmeyq6zlp02d6ew.png)
where:
- M is the magnitude,
- E is the energy released by the earthquake,
- E0 is a reference energy level,
- log represents the common logarithm (base 10).
Given that the first earthquake has a magnitude of 3.9 and the second earthquake has 800 times as much energy as the first, we can find the magnitude of the second earthquake as follows:
Step 1: Express the Magnitude of the First Earthquake
For the first earthquake with magnitude 3.9:
![\[ 3.9 = (2)/(3) \log\left((E_1)/(E_0)\right) \]](https://img.qammunity.org/2024/formulas/mathematics/high-school/v1jzwktx7r0t8nqje11upalfkiy6c7v0dr.png)
where
is the energy of the first earthquake.
Step 2: Solve for

Rearranging the formula, we get:
![\[ \log\left((E_1)/(E_0)\right) = (3)/(2) * 3.9 \]](https://img.qammunity.org/2024/formulas/mathematics/high-school/372bc3rlvco2wvbdqsny40dbpy4rtrxc55.png)
We can then find
by taking the antilogarithm.
Step 3: Calculate the Energy Ratio for the Second Earthquake
The energy of the second earthquake is 800 times that of the first earthquake, so
The magnitude of the second earthquake,
, is:
![\[ M_2 = (2)/(3) \log\left((E_2)/(E_0)\right) = (2)/(3) \log\left((800E_1)/(E_0)\right) \]](https://img.qammunity.org/2024/formulas/mathematics/high-school/2bp85xgmlqtdle6ivd6qhgiqievd9ovgbh.png)
Step 4: Express

We can use the relationship between
from the first earthquake to express

Let's start by calculating
and then use it to find the magnitude of the second earthquake.
The magnitude of the second earthquake, which has 800 times the energy of the first earthquake with a magnitude of 3.9 on the Moment Magnitude Scale (MMS), is approximately 5.84.