Learn Hardcore Turkish: Depremden hemen sonra telefonlarda büyük bir kesinti yaşandı. - Right after the earthquake, there was a major interruption in phone service.

The suffix -den is the ablative case, often translated as “from” or “after” when used with sonra. Here Depremden sonra means “after the earthquake.” Because hemen (“immediately”) comes between Depremden and sonra, you get “immediately after the earthquake.”

What is the function of hemen in Depremden hemen sonra, and could it go elsewhere?

Hemen is an adverb meaning “immediately” or “right away.” In Turkish, it commonly appears directly before sonra to form hemen sonra (“immediately after”). You could also say Hemen depremden sonra without changing the meaning, but Depremden hemen sonra is the most natural word order in reporting events.

Why is telefonlarda plural and in the locative case (-da)?

Telefon means “telephone/phone.” The suffix -lar pluralizes it to telefonlar (“phones”), and -da is the locative case, literally “in/on.” So telefonlarda means “on the phones” or more loosely “in the phone network.” Plural here indicates that the outage affected phones in general, not just one device.

What does büyük bir kesinti mean, and why is bir included?

Büyük means “big” and kesinti is “interruption/outage.” The word bir functions like the English indefinite article “a.” So büyük bir kesinti is “a big interruption.” Including bir makes the noun phrase indefinite. You could also say büyük kesinti yaşandı (“there was a big outage”), dropping bir; the meaning stays almost the same, though adding bir often feels more natural.

What tense and voice is yaşandı, and what does it convey?

Yaşandı is the simple past, 3rd person singular of the verb yaşanmak, which literally means “to be experienced” or “to occur.” In this context it’s an intransitive/middle-voice form meaning “(it) happened” or “was experienced.” So kesinti yaşandı means “an outage occurred.”

Could we replace yaşandı with oldu or meydana geldi? What’s the nuance?

Yes.

Kesinti oldu (“an outage happened”) is very common and simple.
Kesinti meydana geldi (“an outage took place/occurred”) sounds slightly more formal.
Kesinti yaşandı emphasizes the experience of the event—common in news reports. All three are correct; the choice depends on style and nuance.

Why is there no explicit subject in this sentence?

Turkish often drops the subject when it’s clear or impersonal. Here the sentence describes an event (a big outage) rather than an actor doing something. The verb yaşandı itself is impersonal, so no separate subject pronoun is needed.

What is the overall word order, and is it flexible?

The canonical Turkish order is Subject-Object-Verb (S-O-V). Here it’s more like [Time/Condition] – [Place] – [Object] – [Verb]:
“Depremden hemen sonra / telefonlarda / büyük bir kesinti / yaşandı.”
You can move adverbials around for emphasis (e.g., Telefonlarda depremden hemen sonra büyük bir kesinti yaşandı), but the verb typically stays at the end.