Learn Hardcore Japanese: zisin de hurui hondana ga taoremasita. - Because of the earthquake, the old bookshelf fell over.

the place where an action happens (e.g. 学校で勉強します – I study at school), or
the cause / reason when it follows an event or accident (e.g. 雨で試合が中止になりました – The game was canceled because of the rain).

地震 is an event, so 地震で is understood as:

"because of the earthquake"
"the earthquake caused..."

So the sentence is like: "Because of the earthquake, the old bookshelf fell over."

Why is が used after 本棚 instead of は?

が marks the subject of the verb, especially with intransitive verbs like 倒れる (to fall over).

本棚が倒れました。
→ The bookshelf fell over. (stating what actually fell)

If you used は:

本棚は倒れました。
This sets 本棚 as the topic and sounds like:
- "As for the bookshelf, it fell over (as opposed to something else)."
  This would be used if you're contrasting it with something that didn't fall, or you were already talking about the bookshelf.

In a neutral, first-time statement of what happened, が is the natural choice.

What is the difference between 倒れました and 倒しました?

They come from two different verbs:

倒れる (intransitive): to fall over / to collapse
- 本棚が倒れました。
  → The bookshelf fell over. (by itself / due to some cause)
倒す (transitive): to knock something over / to topple something
- 本棚を倒しました。
  → [Someone] knocked over the bookshelf.

In your sentence:

地震で古い本棚が倒れました。
→ The bookshelf fell over because of the earthquake (no human agent expressed).

If you wanted to say "The earthquake knocked over the bookshelf" in a more agent-like way, Japanese usually still prefers the intransitive 倒れる with で showing cause, just like the original sentence.

Why is 古い placed before 本棚? Can it go after, like in English "bookshelf old"?

In Japanese, adjectives that directly modify nouns usually come before the noun.

古い本棚
→ literally "old bookshelf" (adjective + noun)

You cannot say 本棚古い as a noun phrase like "bookshelf old" in English.

Compare:

古い本棚が倒れました。
→ The old bookshelf fell over. (古い directly modifies 本棚)

vs.

本棚は古いです。
→ The bookshelf is old. (古い is a predicate describing 本棚)

So:

Adjective + Noun: 古い本棚 (old bookshelf)
Noun + は + Adjective: 本棚は古いです (the bookshelf is old)

Is 古い本棚 "an old bookshelf" or "the old bookshelf"? Where is "a / the" in Japanese?

Japanese does not have articles like "a" or "the".
古い本棚 can mean:

an old bookshelf
the old bookshelf
old bookshelves (in some contexts)

The correct English article depends on context, not on any specific word in Japanese.

For example:

In a story where there is one specific old bookshelf everyone knows about, 古い本棚 → "the old bookshelf".
If you are introducing it for the first time with no prior context, it may sound more like "an old bookshelf" in English.

Why is there no topic like 私は or うちでは at the beginning? Who does this sentence belong to?

Japanese often omits topics and subjects when they are obvious from context.

If you are talking about what happened at your house, people will naturally understand the unstated topic as something like:
- うちで地震があって、古い本棚が倒れました。
  (At my place there was an earthquake, and the old bookshelf fell over.)

You could say:

うちでは地震で古い本棚が倒れました。
→ At my place, the old bookshelf fell over because of the earthquake.

But in natural conversation or narrative, speakers often drop 私は, うちでは, etc., and just say the core event sentence:
地震で古い本棚が倒れました。

Why is 倒れました in the polite past form -ました instead of plain past 倒れた?

Japanese has two main politeness levels in basic verb forms:

Polite: 倒れました
Plain: 倒れた

You choose based on who you're talking to, not on the sentence content.

Talking to a teacher, colleague, or someone you’re not close to:
- 地震で古い本棚が倒れました。 (polite)
Talking to a close friend or diary-style:
- 地震で古い本棚が倒れた。 (plain)

Both mean the same event; the difference is just politeness level.

Could I use に instead of で, like 地震に古い本棚が倒れました?

地震に古い本棚が倒れました is not natural.

The normal, natural way to express "because of an earthquake" is:

地震で古い本棚が倒れました。

Reasons:

で with an event (地震, 雨, 台風, 火事, etc.) often marks cause:
- 雨で試合が中止になりました。
- 事故で電車が遅れました。

に can mark things like:

time (三時に, 月曜日に)
direction/target (東京に行きます)
indirect object (母にプレゼントをあげます)

Using に after 地震 to mean "because of the earthquake" is incorrect in standard Japanese. Use 地震で.

What exactly does 倒れる mean? Is it "to fall," "to collapse," or "to break"?

倒れる basically means "to topple / to fall over / to collapse" in a physical or figurative sense.

Typical uses:

木が倒れました。
→ A tree fell over / toppled.
建物が倒れました。
→ A building collapsed.
彼は熱で倒れました。
→ He collapsed from a fever.

It emphasizes losing an upright or stable position, not necessarily breaking into pieces.

If you want to stress "broke / got damaged", you might use:

壊れる (to break, to be broken)
- 本棚が壊れました。
  → The bookshelf broke (got damaged).

Your sentence:

倒れました focuses on falling over, not on whether it broke or not.

Could I say 古い本棚は地震で倒れました instead? How would that feel different?

Yes, you can say:

古い本棚は地震で倒れました。

Difference in nuance:

古い本棚が地震で倒れました。
- Neutral statement: "The old bookshelf fell over because of the earthquake."
- Focus on what happened / what fell.
古い本棚は地震で倒れました。
- Topic-comment structure: "As for the old bookshelf, it fell over because of the earthquake."
- Implies:
  - Maybe something else (like a new bookshelf) did not fall.
  - Or you were already talking about that old bookshelf, and this is new information about it.

So は adds a sense of "as for..." or contrast / known topic.

Is the word order fixed? Could I say 古い本棚が地震で倒れました instead?

Yes, you can say:

古い本棚が地震で倒れました。

Both:

地震で古い本棚が倒れました。
古い本棚が地震で倒れました。

are natural.

Subtle nuance:

地震で古い本棚が倒れました。
→ Slightly stronger focus on the cause (the earthquake).
古い本棚が地震で倒れました。
→ Slightly stronger focus on what fell (the old bookshelf).

But in everyday speech, both are fine and the difference is small. Japanese word order is more flexible than English, as long as you keep:

verbs at the end, and
particles (が / を / で / に, etc.) attached to the right words.

How do you read all the kanji in this sentence, and what are their basic meanings?

Reading (with basic meanings):

地震 → じしん (jishin)
- 地: ち – earth, ground
- 震: しん – quake, shake
  → together: earthquake
古い → ふるい (furui)
- 古: ふる – old
本棚 → ほんだな (hondana)
- 本: ほん – book
- 棚: だな – shelf
  → together: bookshelf / bookcase
倒れました → たおれました (taoremashita)
- Dictionary form: 倒れる (たおれる) – to fall over, collapse
- ました: polite past

So the whole sentence is read:

じしんで　ふるい　ほんだなが　たおれました。

If I want to say "The earthquake knocked over my old bookshelf" and make it sound like the earthquake is the "doer," how could I say that?

Japanese usually describes this kind of situation with an intransitive verb and a cause marked by で, like your original sentence:

地震で古い本棚が倒れました。
→ Because of the earthquake, my old bookshelf fell over.

If you really want to treat the earthquake like an active agent, you can use a transitive verb:

地震が古い本棚を倒しました。

But:

This sounds a bit more literal / personifying the earthquake (as if the earthquake is actively doing it).
In natural Japanese, people mostly prefer the intransitive pattern with で:
- 地震で古い本棚が倒れました。

So in normal usage, the original sentence is the most natural way to express "The earthquake knocked over my old bookshelf."