Olay yeri güvenliği beceri rehberinde açıklanıyor.

Because Turkish normally puts the main verb last.

So in Olay yeri güvenliği beceri rehberinde açıklanıyor, the structure is roughly:

• Olay yeri güvenliği = scene safety
• beceri rehberinde = in the skill guide
• açıklanıyor = is being explained / is explained

A very natural English rearrangement would be:

• Scene safety is explained in the skill guide.

Turkish word order is more flexible than English, but putting the verb at the end is the most neutral pattern.

It is a chain of nouns:

• olay = event, incident
• yer = place
• olay yeri = scene of the incident / scene
• güvenlik = safety, security
• olay yeri güvenliği = scene safety / safety of the scene

So this is not a full clause; it is a noun phrase built out of smaller noun combinations.

Because Turkish often forms noun compounds by adding a possessive-type ending to the second noun.

Here:

• olay yeri güvenlik would be incorrect
• olay yeri güvenliği is correct

This pattern is very common:

• okul kapısı = school door
• şehir merkezi = city center
• iş güvenliği = work safety

So güvenliği here does not mean his/her safety in the normal sense. It is part of the compound structure.

Also, the final k in güvenlik changes to ğ before the vowel-initial ending:

• güvenlik → güvenliği

This is a regular sound change in Turkish.

Because olay yeri is a standard indefinite noun compound in Turkish.

Compare:

• olay yeri = incident scene / scene
• olayın yeri = the place of the incident

The first one is the more fixed, label-like expression. It works like a compound noun. The second one sounds more like you are talking about one specific incident and saying the place of that incident.

In technical or official language, olay yeri is the normal expression.

This also contains a noun compound plus a case ending.

Start with:

• beceri = skill
• rehber = guide
• beceri rehberi = skill guide

Then add the locative ending -de / -da meaning in / at / on:

• beceri rehberinde = in the skill guide

Why -nde instead of just -de?

Because rehberi already has the compound ending, and when a case ending is added after that, Turkish uses a buffer n:

• rehberi
  • -de → rehberinde

So beceri rehberinde means in the skill guide.

Because açıklanıyor is passive.

• açıklamak = to explain
• açıklıyor = he/she/it is explaining
• açıklanıyor = it is being explained / it is explained

So the sentence does not mean:

• The skill guide is explaining scene safety

It means:

• Scene safety is explained in the skill guide

The passive is very common in Turkish when the person doing the action is unimportant, unknown, or simply not mentioned.

Not necessarily.

The ending -yor often corresponds to the English present continuous, but in Turkish it is also frequently used for general present situations, especially in modern Turkish.

So açıklanıyor can mean:

• is being explained
• is explained

In a sentence like this, especially in an instructional or formal context, English often translates it more naturally as is explained.

The subject is olay yeri güvenliği.

Since the verb is passive, the thing receiving the action becomes the grammatical subject:

• Olay yeri güvenliği ... açıklanıyor.
• Scene safety ... is explained.

There is no expressed by someone phrase here. Turkish often leaves the agent out in passive sentences.

Because Turkish has no articles like English the and a/an.

Whether something is definite or indefinite usually comes from:

• context
• word order
• the type of noun phrase
• general meaning

So olay yeri güvenliği can be translated naturally into English as scene safety or the safety of the scene, depending on context.

Likewise, beceri rehberinde becomes in the skill guide in good English, even though Turkish does not use a separate word for the.

It is natural, but it sounds formal and technical.

Why?

• It uses several noun compounds: olay yeri güvenliği, beceri rehberi
• It uses the passive: açıklanıyor
• It sounds like language from a manual, guide, training document, or official material

That fits the content very well. In everyday speech, a person might use a less dense structure, but in written instructional Turkish this style is very common.