Deniz kenarındaki tsunami uyarı levhasını fark ettiğimizde güvenli bölgeye koştuk.

The segment -deki turns a location into a “relative adjective,” meaning “that is at…”

1. Start with the compound noun deniz kenarı (“seaside”).
2. Because deniz kenarı ends in a vowel (–ı), you need a buffer n before the locative-relative daki, giving –ndaki.
3. So deniz kenarı-ndaki literally means “the one that is at the seaside.”

This phrase is a three-noun chain with possessive and accusative marking:

1. tsunami (loan noun) + uyarı (“warning”) + levha (“sign”) = tsunami uyarı levhası, “the sign of the warning.”
2. -sı is the 3rd person singular possessive on levha (because levha ends in a, it takes -sı): levha → levha­sı.
3. -nı is the accusative (direct-object) suffix, attached to the now-definite noun levhası (with buffer n): levha­sı → levha­sı­nı.
   Hence tsunami uyarı levhasını = “(we noticed) the tsunami warning sign.”

This is a verb‐based time clause built on fark etmek (“to notice”):
– et = verb root (from the noun fark)
– -ti = past-tense marker
– -ğimiz = 1st person-plural suffix (“we”)
– -de = locative case used on verbs to mean “when”
Putting it together:
et-ti-ğimiz-de → ettiğimizde, so fark ettiğimizde = “when we noticed.”

In Turkish:
• -de on a verb stem (after participle markers) means “at the time when…” (“when”).
• -den on a verb stem means “from the time when…” or “since.”
Here we want “when we noticed…”, so we use ettiğimizde (–de), not ettiğimizden.

güvenli bölgeye is in the dative case, showing motion toward a place: “to the safe zone.”
– bölge ends in e (a front vowel), so the dative suffix is -ye (front variant plus buffer y).
– güvenli is simply an adjective (“safe”) modifying bölgeye.

From the verb koşmak (“to run”):

1. Remove -mak, leaving the stem koş.
2. Add past-tense -du (because o is a back rounded vowel) → koşdu.
3. After a voiceless consonant ş, d becomes t, so koşdu → koştu.
4. Add 1st-person-plural -k → koştu+k = koştuk (“we ran”).